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# IPython reference

Contents

- IPython reference
  - Command-line usage
    - Special Threading Options
    - Regular Options
  - Interactive use
    - Caution for Windows users
    - Magic command system
    - Magic commands
    - Access to the standard Python help
    - Dynamic object information
    - Readline-based features
      - Command line completion
      - Search command history
      - Persistent command history across sessions
      - Autoindent
      - Customizing readline behavior
    - Session logging and restoring
    - System shell access
    - Manual capture of command output
    - System command aliases
    - Recursive reload
    - Verbose and colored exception traceback printouts
    - Input caching system
    - Output caching system
    - Directory history
    - Automatic parentheses and quotes
    - Automatic parentheses
    - Automatic quoting
  - IPython as your default Python environment
  - Embedding IPython
  - Using the Python debugger (pdb)
    - Running entire programs via pdb
    - Automatic invocation of pdb on exceptions
  - Extensions for syntax processing
    - Pasting of code starting with ‘>>> ‘ or ‘... ‘
    - Input of physical quantities with units
  - Threading support
    - Tk issues
    - I/O pitfalls
  - Interactive demos with IPython
  - Plotting with matplotlib

## Command-line usage

You start IPython with the command:

    $ ipython [options] files

If invoked with no options, it executes all the files listed in sequence and drops you into the interpreter while still acknowledging any options you may have set in your ipythonrc file. This behavior is different from standard Python, which when called as python -i will only execute one file and ignore your configuration setup.

Please note that some of the configuration options are not available at the command line, simply because they are not practical here. Look into your ipythonrc configuration file for details on those. This file typically installed in the $HOME/.ipython directory. For Windows users, $HOME resolves to C:\Documents and Settings\YourUserName in most instances. In the rest of this text, we will refer to this directory as IPYTHONDIR.

### Special Threading Options

The following special options are ONLY valid at the beginning of the command line, and not later. This is because they control the initial- ization of ipython itself, before the normal option-handling mechanism is active.

> -gthread, -qthread, -q4thread, -wthread, -pylab:

>   Only one of these can be given, and it can only be given as the first option passed to IPython (it will have no effect in any other position). They provide threading support for the GTK, Qt (versions 3 and 4) and WXPython toolkits, and for the matplotlib library.

>   With any of the first four options, IPython starts running a separate thread for the graphical toolkit’s operation, so that you can open and control graphical elements from within an IPython command line, without blocking. All four provide essentially the same functionality, respectively for GTK, Qt3, Qt4 and WXWidgets (via their Python interfaces).

>   Note that with -wthread, you can additionally use the -wxversion option to request a specific version of wx to be used. This requires that you have the wxversion Python module installed, which is part of recent wxPython distributions.

>   If -pylab is given, IPython loads special support for the mat plotlib library (http://matplotlib.sourceforge.net), allowing interactive usage of any of its backends as defined in the user’s ~/.matplotlib/matplotlibrc file. It automatically activates GTK, Qt or WX threading for IPyhton if the choice of matplotlib backend requires it. It also modifies the %run command to correctly execute (without blocking) any matplotlib-based script which calls show() at the end.

> `-tk` | The -g/q/q4/wthread options, and -pylab (if matplotlib is configured to use GTK, Qt3, Qt4 or WX), will normally block Tk graphical interfaces. This means that when either GTK, Qt or WX threading is active, any attempt to open a Tk GUI will result in a dead window, and possibly cause the Python interpreter to crash. An extra option, -tk, is available to address this issue. It can only be given as a second option after any of the above (-gthread, -wthread or -pylab). If -tk is given, IPython will try to coordinate Tk threading with GTK, Qt or WX. This is however potentially unreliable, and you will have to test on your platform and Python configuration to determine whether it works for you. Debian users have reported success, apparently due to the fact that Debian builds all of Tcl, Tk, Tkinter and Python with pthreads support. Under other Linux environments (such as Fedora Core 2/3), this option has caused random crashes and lockups of the Python interpreter. Under other operating systems (Mac OSX and Windows), you’ll need to try it to find out, since currently no user reports are available. There is unfortunately no way for IPython to determine at run time whether -tk will work reliably or not, so you will need to do some experiments before relying on it for regular work.

### Regular Options

After the above threading options have been given, regular options can follow in any order. All options can be abbreviated to their shortest non-ambiguous form and are case-sensitive. One or two dashes can be used. Some options have an alternate short form, indicated after a `|`.

Most options can also be set from your ipythonrc configuration file. See the provided example for more details on what the options do. Options given at the command line override the values set in the ipythonrc file.

All options with a [no] prepended can be specified in negated form (-nooption instead of -option) to turn the feature off.

> `-help` | print a help message and exit.
> `-pylab` | this can only be given as the first option passed to IPython (it will have no effect in any other position). It adds special support for the matplotlib library (http://matplotlib.sourceforge.ne), allowing interactive usage of any of its backends as defined in the user’s .matplotlibrc file. It automatically activates GTK or WX threading for IPyhton if the choice of matplotlib backend requires it. It also modifies the %run command to correctly execute (without blocking) any matplotlib-based script which calls show() at the end. See Matplotlib support for more details.

> -autocall <val>
>   Make IPython automatically call any callable object even if you didn’t type explicit parentheses. For example, ‘str 43’ becomes ‘str(43)’ automatically. The value can be ‘0’ to disable the feature, ‘1’ for smart autocall, where it is not applied if there are no more arguments on the line, and ‘2’ for full autocall, where all callable objects are automatically called (even if no arguments are present). The default is ‘1’.
> -[no]autoindent
>   Turn automatic indentation on/off.
> -[no]automagic
>   make magic commands automatic (without needing their first character to be %). Type %magic at the IPython prompt for more information.
> -[no]autoedit_syntax
>   When a syntax error occurs after editing a file, automatically open the file to the trouble causing line for convenient fixing.

> -[no]banner Print the initial information banner (default on).

> `-c <command>` | execute the given command string. This is similar to the -c option in the normal Python interpreter.

> -cache_size, cs <n>
>   size of the output cache (maximum number of entries to hold in memory). The default is 1000, you can change it permanently in your config file. Setting it to 0 completely disables the caching system, and the minimum value accepted is 20 (if you provide a value less than 20, it is reset to 0 and a warning is issued) This limit is defined because otherwise you’ll spend more time re-flushing a too small cache than working.
> -classic, cl
>   Gives IPython a similar feel to the classic Python prompt.
> -colors <scheme>
>   Color scheme for prompts and exception reporting. Currently implemented: NoColor, Linux and LightBG.
> -[no]color_info

>   IPython can display information about objects via a set of functions, and optionally can use colors for this, syntax highlighting source code and various other elements. However, because this information is passed through a pager (like ‘less’) and many pagers get confused with color codes, this option is off by default. You can test it and turn it on permanently in your ipythonrc file if it works for you. As a reference, the ‘less’ pager supplied with Mandrake 8.2 works ok, but that in RedHat 7.2 doesn’t.

>   Test it and turn it on permanently if it works with your system. The magic function %color_info allows you to toggle this interactively for testing.

> -[no]debug
>   Show information about the loading process. Very useful to pin down problems with your configuration files or to get details about session restores.
> -[no]deep_reload:

>   IPython can use the deep_reload module which reloads changes in modules recursively (it replaces the reload() function, so you don’t need to change anything to use it). deep_reload() forces a full reload of modules whose code may have changed, which the default reload() function does not.

>   When deep_reload is off, IPython will use the normal reload(), but deep_reload will still be available as dreload(). This feature is off by default [which means that you have both normal reload() and dreload()].

> -editor <name>
>   Which editor to use with the %edit command. By default, IPython will honor your EDITOR environment variable (if not set, vi is the Unix default and notepad the Windows one). Since this editor is invoked on the fly by IPython and is meant for editing small code snippets, you may want to use a small, lightweight editor here (in case your default EDITOR is something like Emacs).
> -ipythondir <name>
>   name of your IPython configuration directory IPYTHONDIR. This can also be specified through the environment variable IPYTHONDIR.
> -log, l
>   generate a log file of all input. The file is named ipython_log.py in your current directory (which prevents logs from multiple IPython sessions from trampling each other). You can use this to later restore a session by loading your logfile as a file to be executed with option -logplay (see below).

> -logfile, lf <name> specify the name of your logfile.

> -logplay, lp <name>

> > you can replay a previous log. For restoring a session as close as possible to the state you left it in, use this option (don’t just run the logfile). With -logplay, IPython will try to reconstruct the previous working environment in full, not just execute the commands in the logfile.

> > When a session is restored, logging is automatically turned on again with the name of the logfile it was invoked with (it is read from the log header). So once you’ve turned logging on for a session, you can quit IPython and reload it as many times as you want and it will continue to log its history and restore from the beginning every time.

> > Caveats: there are limitations in this option. The history variables _i*,_* and _dh don’t get restored properly. In the future we will try to implement full session saving by writing and retrieving a ‘snapshot’ of the memory state of IPython. But our first attempts failed because of inherent limitations of Python’s Pickle module, so this may have to wait.

> -[no]messages
>   Print messages which IPython collects about its startup process (default on).
> -[no]pdb
>   Automatically call the pdb debugger after every uncaught exception. If you are used to debugging using pdb, this puts you automatically inside of it after any call (either in IPython or in code called by it) which triggers an exception which goes uncaught.

> `-pydb` | Makes IPython use the third party “pydb” package as debugger, instead of pdb. Requires that pydb is installed.

> -[no]pprint
>   ipython can optionally use the pprint (pretty printer) module for displaying results. pprint tends to give a nicer display of nested data structures. If you like it, you can turn it on permanently in your config file (default off).

> -profile, p <name>

> > assume that your config file is ipythonrc-<name> or ipy_profile_<name>.py (looks in current dir first, then in IPYTHONDIR). This is a quick way to keep and load multiple config files for different tasks, especially if you use the include option of config files. You can keep a basic IPYTHONDIR/ipythonrc file and then have other ‘profiles’ which include this one and load extra things for particular tasks. For example:

> > 1. $HOME/.ipython/ipythonrc : load basic things you always want.
> > 2. $HOME/.ipython/ipythonrc-math : load (1) and basic math-related modules.
> > 3. $HOME/.ipython/ipythonrc-numeric : load (1) and Numeric and plotting modules.

> > Since it is possible to create an endless loop by having circular file inclusions, IPython will stop if it reaches 15 recursive inclusions.

> -prompt_in1, pi1 <string>

> > Specify the string used for input prompts. Note that if you are using numbered prompts, the number is represented with a ‘#’ in the string. Don’t forget to quote strings with spaces embedded in them. Default: ‘In [#]:’. The prompts section discusses in detail all the available escapes to customize your prompts.

> -prompt_in2, pi2 <string>
>   Similar to the previous option, but used for the continuation prompts. The special sequence ‘D’ is similar to ‘#’, but with all digits replaced dots (so you can have your continuation prompt aligned with your input prompt). Default: ‘ .D.:’ (note three spaces at the start for alignment with ‘In [#]’).
> -prompt_out,po <string>
>   String used for output prompts, also uses numbers like prompt_in1. Default: ‘Out[#]:’

> `-quick` | start in bare bones mode (no config file loaded).

> -rcfile <name>

>   name of your IPython resource configuration file. Normally IPython loads ipythonrc (from current directory) or IPYTHONDIR/ipythonrc.

>   If the loading of your config file fails, IPython starts with a bare bones configuration (no modules loaded at all).

> -[no]readline

>   use the readline library, which is needed to support name completion and command history, among other things. It is enabled by default, but may cause problems for users of X/Emacs in Python comint or shell buffers.

>   Note that X/Emacs ‘eterm’ buffers (opened with M-x term) support IPython’s readline and syntax coloring fine, only ‘emacs’ (M-x shell and C-c !) buffers do not.

> -screen_length, sl <n>

>   number of lines of your screen. This is used to control printing of very long strings. Strings longer than this number of lines will be sent through a pager instead of directly printed.

>   The default value for this is 0, which means IPython will auto-detect your screen size every time it needs to print certain potentially long strings (this doesn’t change the behavior of the ‘print’ keyword, it’s only triggered internally). If for some reason this isn’t working well (it needs curses support), specify it yourself. Otherwise don’t change the default.

> -separate_in, si <string>

> > separator before input prompts. Default: ‘n’

> -separate_out, so <string>
>   separator before output prompts. Default: nothing.
> -separate_out2, so2
>   separator after output prompts. Default: nothing. For these three options, use the value 0 to specify no separator.

> `-nosep` | shorthand for ‘-SeparateIn 0 -SeparateOut 0 -SeparateOut2 0’. Simply removes all input/output separators.
> `-upgrade` | allows you to upgrade your IPYTHONDIR configuration when you install a new version of IPython. Since new versions may include new command line options or example files, this copies updated ipythonrc-type files. However, it backs up (with a .old extension) all files which it overwrites so that you can merge back any customizations you might have in your personal files. Note that you should probably use %upgrade instead, it’s a safer alternative.
> `-Version` | print version information and exit.

> -wxversion <string>
>   Select a specific version of wxPython (used in conjunction with -wthread). Requires the wxversion module, part of recent wxPython distributions

> -xmode <modename>

> > Mode for exception reporting.

> > Valid modes: Plain, Context and Verbose.

> > - Plain: similar to python’s normal traceback printing.
> > - Context: prints 5 lines of context source code around each line in the traceback.
> > - Verbose: similar to Context, but additionally prints the variables currently visible where the exception happened (shortening their strings if too long). This can potentially be very slow, if you happen to have a huge data structure whose string representation is complex to compute. Your computer may appear to freeze for a while with cpu usage at 100%. If this occurs, you can cancel the traceback with Ctrl-C (maybe hitting it more than once).

## Interactive use

Warning: IPython relies on the existence of a global variable called _ip which controls the shell itself. If you redefine _ip to anything, bizarre behavior will quickly occur.

Other than the above warning, IPython is meant to work as a drop-in replacement for the standard interactive interpreter. As such, any code which is valid python should execute normally under IPython (cases where this is not true should be reported as bugs). It does, however, offer many features which are not available at a standard python prompt. What follows is a list of these.

### Caution for Windows users

Windows, unfortunately, uses the ‘’ character as a path separator. This is a terrible choice, because ‘’ also represents the escape character in most modern programming languages, including Python. For this reason, using ‘/’ character is recommended if you have problems with `\`. However, in Windows commands ‘/’ flags options, so you can not use it for the root directory. This means that paths beginning at the root must be typed in a contrived manner like: `%copy \opt/foo/bar.txt \tmp`

### Magic command system

IPython will treat any line whose first character is a % as a special call to a ‘magic’ function. These allow you to control the behavior of IPython itself, plus a lot of system-type features. They are all prefixed with a % character, but parameters are given without parentheses or quotes.

Example: typing ‘%cd mydir’ (without the quotes) changes you working directory to ‘mydir’, if it exists.

If you have ‘automagic’ enabled (in your ipythonrc file, via the command line option -automagic or with the %automagic function), you don’t need to type in the % explicitly. IPython will scan its internal list of magic functions and call one if it exists. With automagic on you can then just type ‘cd mydir’ to go to directory ‘mydir’. The automagic system has the lowest possible precedence in name searches, so defining an identifier with the same name as an existing magic function will shadow it for automagic use. You can still access the shadowed magic function by explicitly using the % character at the beginning of the line.

An example (with automagic on) should clarify all this:

    In [1]: cd ipython # %cd is called by automagic

    /home/fperez/ipython

    In [2]: cd=1 # now cd is just a variable

    In [3]: cd .. # and doesn't work as a function anymore

    ------------------------------

        File "<console>", line 1

          cd ..

              ^

    SyntaxError: invalid syntax

    In [4]: %cd .. # but %cd always works

    /home/fperez

    In [5]: del cd # if you remove the cd variable

    In [6]: cd ipython # automagic can work again

    /home/fperez/ipython

You can define your own magic functions to extend the system. The following example defines a new magic command, %impall:

    import IPython.ipapi

    ip = IPython.ipapi.get()

    def doimp(self, arg):

        ip = self.api

        ip.ex("import %s; reload(%s); from %s import *" % (

        arg,arg,arg)

        )

    ip.expose_magic('impall', doimp)

You can also define your own aliased names for magic functions. In your ipythonrc file, placing a line like:

execute __IP.magic_cl = __IP.magic_clear

will define %cl as a new name for %clear.

Type %magic for more information, including a list of all available magic functions at any time and their docstrings. You can also type %magic_function_name? (see sec. 6.4 <#sec:dyn-object-info> for information on the ‘?’ system) to get information about any particular magic function you are interested in.

### Magic commands

The rest of this section is automatically generated for each release from the docstrings in the IPython code. Therefore the formatting is somewhat minimal, but this method has the advantage of having information always in sync with the code.

A list of all the magic commands available in IPython’s default installation follows. This is similar to what you’ll see by simply typing %magic at the prompt, but that will also give you information about magic commands you may have added as part of your personal customizations.

%Exit:

    Exit IPython without confirmation.

%Pprint:

    Toggle pretty printing on/off.

%alias:

    Define an alias for a system command.

    '%alias alias_name cmd' defines 'alias_name' as an alias for 'cmd'

    Then, typing 'alias_name params' will execute the system command 'cmd
    params' (from your underlying operating system).

    Aliases have lower precedence than magic functions and Python normal
    variables, so if 'foo' is both a Python variable and an alias, the
    alias can not be executed until 'del foo' removes the Python variable.

    You can use the %l specifier in an alias definition to represent the
    whole line when the alias is called.  For example:

      In [2]: alias all echo "Input in brackets: <%l>"\
      In [3]: all hello world\
      Input in brackets: <hello world>

    You can also define aliases with parameters using %s specifiers (one
    per parameter):

      In [1]: alias parts echo first %s second %s\
      In [2]: %parts A B\
      first A second B\
      In [3]: %parts A\
      Incorrect number of arguments: 2 expected.\
      parts is an alias to: 'echo first %s second %s'

    Note that %l and %s are mutually exclusive.  You can only use one or
    the other in your aliases.

    Aliases expand Python variables just like system calls using ! or !!
    do: all expressions prefixed with '$' get expanded.  For details of
    the semantic rules, see PEP-215:
    http://www.python.org/peps/pep-0215.html.  This is the library used by
    IPython for variable expansion.  If you want to access a true shell
    variable, an extra $ is necessary to prevent its expansion by IPython:

    In [6]: alias show echo\
    In [7]: PATH='A Python string'\
    In [8]: show $PATH\
    A Python string\
    In [9]: show $$PATH\
    /usr/local/lf9560/bin:/usr/local/intel/compiler70/ia32/bin:...

    You can use the alias facility to acess all of $PATH.  See the %rehash
    and %rehashx functions, which automatically create aliases for the
    contents of your $PATH.

    If called with no parameters, %alias prints the current alias table.

%autocall:

    Make functions callable without having to type parentheses.

    Usage:

       %autocall [mode]

    The mode can be one of: 0->Off, 1->Smart, 2->Full.  If not given, the
    value is toggled on and off (remembering the previous state).

    In more detail, these values mean:

    0 -> fully disabled

    1 -> active, but do not apply if there are no arguments on the line.

    In this mode, you get:

    In [1]: callable
    Out[1]: <built-in function callable>

    In [2]: callable 'hello'
    ------> callable('hello')
    Out[2]: False

    2 -> Active always.  Even if no arguments are present, the callable
    object is called:

    In [4]: callable
    ------> callable()

    Note that even with autocall off, you can still use '/' at the start of
    a line to treat the first argument on the command line as a function
    and add parentheses to it:

    In [8]: /str 43
    ------> str(43)
    Out[8]: '43'

%autoindent:

    Toggle autoindent on/off (if available).

%automagic:

    Make magic functions callable without having to type the initial %.

    Without argumentsl toggles on/off (when off, you must call it as
    %automagic, of course).  With arguments it sets the value, and you can
    use any of (case insensitive):

     - on,1,True: to activate

     - off,0,False: to deactivate.

    Note that magic functions have lowest priority, so if there's a
    variable whose name collides with that of a magic fn, automagic won't
    work for that function (you get the variable instead). However, if you
    delete the variable (del var), the previously shadowed magic function
    becomes visible to automagic again.

%bg:

    Run a job in the background, in a separate thread.

    For example,

      %bg myfunc(x,y,z=1)

    will execute 'myfunc(x,y,z=1)' in a background thread.  As soon as the
    execution starts, a message will be printed indicating the job
    number.  If your job number is 5, you can use

      myvar = jobs.result(5)  or  myvar = jobs[5].result

    to assign this result to variable 'myvar'.

    IPython has a job manager, accessible via the 'jobs' object.  You can
    type jobs? to get more information about it, and use jobs.<TAB> to see
    its attributes.  All attributes not starting with an underscore are
    meant for public use.

    In particular, look at the jobs.new() method, which is used to create
    new jobs.  This magic %bg function is just a convenience wrapper
    around jobs.new(), for expression-based jobs.  If you want to create a
    new job with an explicit function object and arguments, you must call
    jobs.new() directly.

    The jobs.new docstring also describes in detail several important
    caveats associated with a thread-based model for background job
    execution.  Type jobs.new? for details.

    You can check the status of all jobs with jobs.status().

    The jobs variable is set by IPython into the Python builtin namespace.
    If you ever declare a variable named 'jobs', you will shadow this
    name.  You can either delete your global jobs variable to regain
    access to the job manager, or make a new name and assign it manually
    to the manager (stored in IPython's namespace).  For example, to
    assign the job manager to the Jobs name, use:

      Jobs = __builtins__.jobs

%bookmark:

    Manage IPython's bookmark system.

    %bookmark <name>       - set bookmark to current dir
    %bookmark <name> <dir> - set bookmark to <dir>
    %bookmark -l           - list all bookmarks
    %bookmark -d <name>    - remove bookmark
    %bookmark -r           - remove all bookmarks

    You can later on access a bookmarked folder with:
      %cd -b <name>
    or simply '%cd <name>' if there is no directory called <name> AND
    there is such a bookmark defined.

    Your bookmarks persist through IPython sessions, but they are
    associated with each profile.

%cd:

    Change the current working directory.

    This command automatically maintains an internal list of directories
    you visit during your IPython session, in the variable _dh. The
    command %dhist shows this history nicely formatted. You can also
    do 'cd -<tab>' to see directory history conveniently.

    Usage:

      cd 'dir': changes to directory 'dir'.

      cd -: changes to the last visited directory.

      cd -<n>: changes to the n-th directory in the directory history.

      cd -b <bookmark_name>: jump to a bookmark set by %bookmark
         (note: cd <bookmark_name> is enough if there is no
          directory <bookmark_name>, but a bookmark with the name exists.)
          'cd -b <tab>' allows you to tab-complete bookmark names.

    Options:

    -q: quiet.  Do not print the working directory after the cd command is
    executed.  By default IPython's cd command does print this directory,
    since the default prompts do not display path information.

    Note that !cd doesn't work for this purpose because the shell where
    !command runs is immediately discarded after executing 'command'.

%clear:

         Clear various data (e.g. stored history data)

    %clear out - clear output history
    %clear in  - clear input history
    %clear shadow_compress - Compresses shadow history (to speed up ipython)
    %clear shadow_nuke - permanently erase all entries in shadow history
    %clear dhist - clear dir history

%color_info:

    Toggle color_info.

    The color_info configuration parameter controls whether colors are
    used for displaying object details (by things like %psource, %pfile or
    the '?' system). This function toggles this value with each call.

    Note that unless you have a fairly recent pager (less works better
    than more) in your system, using colored object information displays
    will not work properly. Test it and see.

%colors:

    Switch color scheme for prompts, info system and exception handlers.

    Currently implemented schemes: NoColor, Linux, LightBG.

    Color scheme names are not case-sensitive.

%cpaste:

    Allows you to paste & execute a pre-formatted code block from clipboard

    You must terminate the block with '--' (two minus-signs) alone on the
    line. You can also provide your own sentinel with '%paste -s %%' ('%%'
    is the new sentinel for this operation)

    The block is dedented prior to execution to enable execution of method
    definitions. '>' and '+' characters at the beginning of a line are
    ignored, to allow pasting directly from e-mails or diff files. The
    executed block is also assigned to variable named 'pasted_block' for
    later editing with '%edit pasted_block'.

    You can also pass a variable name as an argument, e.g. '%cpaste foo'.
    This assigns the pasted block to variable 'foo' as string, without
    dedenting or executing it.

    Do not be alarmed by garbled output on Windows (it's a readline bug).
    Just press enter and type -- (and press enter again) and the block
    will be what was just pasted.

    IPython statements (magics, shell escapes) are not supported (yet).

%debug:

    Activate the interactive debugger in post-mortem mode.

    If an exception has just occurred, this lets you inspect its stack
    frames interactively.  Note that this will always work only on the last
    traceback that occurred, so you must call this quickly after an
    exception that you wish to inspect has fired, because if another one
    occurs, it clobbers the previous one.

    If you want IPython to automatically do this on every exception, see
    the %pdb magic for more details.

%dhist:

    Print your history of visited directories.

    %dhist       -> print full history\
    %dhist n     -> print last n entries only\
    %dhist n1 n2 -> print entries between n1 and n2 (n1 not included)\

    This history is automatically maintained by the %cd command, and
    always available as the global list variable _dh. You can use %cd -<n>
    to go to directory number <n>.

    Note that most of time, you should view directory history by entering
    cd -<TAB>.

%dirs:

    Return the current directory stack.

%doctest_mode:

    Toggle doctest mode on and off.

    This mode allows you to toggle the prompt behavior between normal
    IPython prompts and ones that are as similar to the default IPython
    interpreter as possible.

    It also supports the pasting of code snippets that have leading '>>>'
    and '...' prompts in them.  This means that you can paste doctests from
    files or docstrings (even if they have leading whitespace), and the
    code will execute correctly.  You can then use '%history -tn' to see
    the translated history without line numbers; this will give you the
    input after removal of all the leading prompts and whitespace, which
    can be pasted back into an editor.

    With these features, you can switch into this mode easily whenever you
    need to do testing and changes to doctests, without having to leave
    your existing IPython session.

%ed:

    Alias to %edit.

%edit:

    Bring up an editor and execute the resulting code.

    Usage:
      %edit [options] [args]

    %edit runs IPython's editor hook.  The default version of this hook is
    set to call the __IPYTHON__.rc.editor command.  This is read from your
    environment variable $EDITOR.  If this isn't found, it will default to
    vi under Linux/Unix and to notepad under Windows.  See the end of this
    docstring for how to change the editor hook.

    You can also set the value of this editor via the command line option
    '-editor' or in your ipythonrc file. This is useful if you wish to use
    specifically for IPython an editor different from your typical default
    (and for Windows users who typically don't set environment variables).

    This command allows you to conveniently edit multi-line code right in
    your IPython session.

    If called without arguments, %edit opens up an empty editor with a
    temporary file and will execute the contents of this file when you
    close it (don't forget to save it!).

    Options:

    -n <number>: open the editor at a specified line number.  By default,
    the IPython editor hook uses the unix syntax 'editor +N filename', but
    you can configure this by providing your own modified hook if your
    favorite editor supports line-number specifications with a different
    syntax.

    -p: this will call the editor with the same data as the previous time
    it was used, regardless of how long ago (in your current session) it
    was.

    -r: use 'raw' input.  This option only applies to input taken from the
    user's history.  By default, the 'processed' history is used, so that
    magics are loaded in their transformed version to valid Python.  If
    this option is given, the raw input as typed as the command line is
    used instead.  When you exit the editor, it will be executed by
    IPython's own processor.

    -x: do not execute the edited code immediately upon exit. This is
    mainly useful if you are editing programs which need to be called with
    command line arguments, which you can then do using %run.

    Arguments:

    If arguments are given, the following possibilites exist:

    - The arguments are numbers or pairs of colon-separated numbers (like
    1 4:8 9). These are interpreted as lines of previous input to be
    loaded into the editor. The syntax is the same of the %macro command.

    - If the argument doesn't start with a number, it is evaluated as a
    variable and its contents loaded into the editor. You can thus edit
    any string which contains python code (including the result of
    previous edits).

    - If the argument is the name of an object (other than a string),
    IPython will try to locate the file where it was defined and open the
    editor at the point where it is defined. You can use `%edit function`
    to load an editor exactly at the point where 'function' is defined,
    edit it and have the file be executed automatically.

    If the object is a macro (see %macro for details), this opens up your
    specified editor with a temporary file containing the macro's data.
    Upon exit, the macro is reloaded with the contents of the file.

    Note: opening at an exact line is only supported under Unix, and some
    editors (like kedit and gedit up to Gnome 2.8) do not understand the
    '+NUMBER' parameter necessary for this feature. Good editors like
    (X)Emacs, vi, jed, pico and joe all do.

    - If the argument is not found as a variable, IPython will look for a
    file with that name (adding .py if necessary) and load it into the
    editor. It will execute its contents with execfile() when you exit,
    loading any code in the file into your interactive namespace.

    After executing your code, %edit will return as output the code you
    typed in the editor (except when it was an existing file). This way
    you can reload the code in further invocations of %edit as a variable,
    via _<NUMBER> or Out[<NUMBER>], where <NUMBER> is the prompt number of
    the output.

    Note that %edit is also available through the alias %ed.

    This is an example of creating a simple function inside the editor and
    then modifying it. First, start up the editor:

    In [1]: ed\
    Editing... done. Executing edited code...\
    Out[1]: 'def foo():\n    print "foo() was defined in an editing session"\n'

    We can then call the function foo():

    In [2]: foo()\
    foo() was defined in an editing session

    Now we edit foo.  IPython automatically loads the editor with the
    (temporary) file where foo() was previously defined:

    In [3]: ed foo\
    Editing... done. Executing edited code...

    And if we call foo() again we get the modified version:

    In [4]: foo()\
    foo() has now been changed!

    Here is an example of how to edit a code snippet successive
    times. First we call the editor:

    In [8]: ed\
    Editing... done. Executing edited code...\
    hello\
    Out[8]: "print 'hello'\n"

    Now we call it again with the previous output (stored in _):

    In [9]: ed _\
    Editing... done. Executing edited code...\
    hello world\
    Out[9]: "print 'hello world'\n"

    Now we call it with the output #8 (stored in _8, also as Out[8]):

    In [10]: ed _8\
    Editing... done. Executing edited code...\
    hello again\
    Out[10]: "print 'hello again'\n"

    Changing the default editor hook:

    If you wish to write your own editor hook, you can put it in a
    configuration file which you load at startup time.  The default hook
    is defined in the IPython.hooks module, and you can use that as a
    starting example for further modifications.  That file also has
    general instructions on how to set a new hook for use once you've
    defined it.

%env:

    List environment variables.

%exit:

    Exit IPython, confirming if configured to do so.

    You can configure whether IPython asks for confirmation upon exit by
    setting the confirm_exit flag in the ipythonrc file.

%hist:

    Alternate name for %history.

%history:

        Print input history (_i<n> variables), with most recent last.

    %history       -> print at most 40 inputs (some may be multi-line)\
    %history n     -> print at most n inputs\
    %history n1 n2 -> print inputs between n1 and n2 (n2 not included)\

    Each input's number <n> is shown, and is accessible as the
    automatically generated variable _i<n>.  Multi-line statements are
    printed starting at a new line for easy copy/paste.

    Options:

      -n: do NOT print line numbers. This is useful if you want to get a
      printout of many lines which can be directly pasted into a text
      editor.

      This feature is only available if numbered prompts are in use.

      -t: (default) print the 'translated' history, as IPython understands it.
      IPython filters your input and converts it all into valid Python source
      before executing it (things like magics or aliases are turned into
      function calls, for example). With this option, you'll see the native
      history instead of the user-entered version: '%cd /' will be seen as
      '_ip.magic("%cd /")' instead of '%cd /'.

      -r: print the 'raw' history, i.e. the actual commands you typed.

      -g: treat the arg as a pattern to grep for in (full) history.
      This includes the "shadow history" (almost all commands ever written).
      Use '%hist -g' to show full shadow history (may be very long).
      In shadow history, every index nuwber starts with 0.

      -f FILENAME: instead of printing the output to the screen, redirect it to
       the given file.  The file is always overwritten, though IPython asks for
       confirmation first if it already exists.

%logoff:

    Temporarily stop logging.

    You must have previously started logging.

%logon:

    Restart logging.

    This function is for restarting logging which you've temporarily
    stopped with %logoff. For starting logging for the first time, you
    must use the %logstart function, which allows you to specify an
    optional log filename.

%logstart:

    Start logging anywhere in a session.

    %logstart [-o|-r|-t] [log_name [log_mode]]

    If no name is given, it defaults to a file named 'ipython_log.py' in your
    current directory, in 'rotate' mode (see below).

    '%logstart name' saves to file 'name' in 'backup' mode.  It saves your
    history up to that point and then continues logging.

    %logstart takes a second optional parameter: logging mode. This can be one
    of (note that the modes are given unquoted):\
      append: well, that says it.\
      backup: rename (if exists) to name~ and start name.\
      global: single logfile in your home dir, appended to.\
      over  : overwrite existing log.\
      rotate: create rotating logs name.1~, name.2~, etc.

    Options:

      -o: log also IPython's output.  In this mode, all commands which
      generate an Out[NN] prompt are recorded to the logfile, right after
      their corresponding input line.  The output lines are always
      prepended with a '#[Out]# ' marker, so that the log remains valid
      Python code.

      Since this marker is always the same, filtering only the output from
      a log is very easy, using for example a simple awk call:

        awk -F'#\[Out\]# ' '{if($2) {print $2}}' ipython_log.py

      -r: log 'raw' input.  Normally, IPython's logs contain the processed
      input, so that user lines are logged in their final form, converted
      into valid Python.  For example, %Exit is logged as
      '_ip.magic("Exit").  If the -r flag is given, all input is logged
      exactly as typed, with no transformations applied.

      -t: put timestamps before each input line logged (these are put in
      comments).

%logstate:

    Print the status of the logging system.

%logstop:

    Fully stop logging and close log file.

    In order to start logging again, a new %logstart call needs to be made,
    possibly (though not necessarily) with a new filename, mode and other
    options.

%lsmagic:

    List currently available magic functions.

%macro:

    Define a set of input lines as a macro for future re-execution.

    Usage:\
      %macro [options] name n1-n2 n3-n4 ... n5 .. n6 ...

    Options:

      -r: use 'raw' input.  By default, the 'processed' history is used,
      so that magics are loaded in their transformed version to valid
      Python.  If this option is given, the raw input as typed as the
      command line is used instead.

    This will define a global variable called `name` which is a string
    made of joining the slices and lines you specify (n1,n2,... numbers
    above) from your input history into a single string. This variable
    acts like an automatic function which re-executes those lines as if
    you had typed them. You just type 'name' at the prompt and the code
    executes.

    The notation for indicating number ranges is: n1-n2 means 'use line
    numbers n1,...n2' (the endpoint is included).  That is, '5-7' means
    using the lines numbered 5,6 and 7.

    Note: as a 'hidden' feature, you can also use traditional python slice
    notation, where N:M means numbers N through M-1.

    For example, if your history contains (%hist prints it):

      44: x=1\
      45: y=3\
      46: z=x+y\
      47: print x\
      48: a=5\
      49: print 'x',x,'y',y\

    you can create a macro with lines 44 through 47 (included) and line 49
    called my_macro with:

      In [51]: %macro my_macro 44-47 49

    Now, typing `my_macro` (without quotes) will re-execute all this code
    in one pass.

    You don't need to give the line-numbers in order, and any given line
    number can appear multiple times. You can assemble macros with any
    lines from your input history in any order.

    The macro is a simple object which holds its value in an attribute,
    but IPython's display system checks for macros and executes them as
    code instead of printing them when you type their name.

    You can view a macro's contents by explicitly printing it with:

      'print macro_name'.

    For one-off cases which DON'T contain magic function calls in them you
    can obtain similar results by explicitly executing slices from your
    input history with:

      In [60]: exec In[44:48]+In[49]

%magic:

    Print information about the magic function system.

%mglob:

            This program allows specifying filenames with "mglob" mechanism.
    Supported syntax in globs (wilcard matching patterns)::

     *.cpp ?ellowo*
         - obvious. Differs from normal glob in that dirs are not included.
           Unix users might want to write this as: "*.cpp" "?ellowo*"
     rec:/usr/share=*.txt,*.doc
         - get all *.txt and *.doc under /usr/share,
           recursively
     rec:/usr/share
         - All files under /usr/share, recursively
     rec:*.py
         - All .py files under current working dir, recursively
     foo
         - File or dir foo
     !*.bak readme*
         - readme*, exclude files ending with .bak
     !.svn/ !.hg/ !*_Data/ rec:.
         - Skip .svn, .hg, foo_Data dirs (and their subdirs) in recurse.
           Trailing / is the key, \ does not work!
     dir:foo
         - the directory foo if it exists (not files in foo)
     dir:*
         - all directories in current folder
     foo.py bar.* !h* rec:*.py
         - Obvious. !h* exclusion only applies for rec:*.py.
           foo.py is *not* included twice.
     @filelist.txt
         - All files listed in 'filelist.txt' file, on separate lines.

%page:

    Pretty print the object and display it through a pager.

    %page [options] OBJECT

    If no object is given, use _ (last output).

    Options:

      -r: page str(object), don't pretty-print it.

%pdb:

    Control the automatic calling of the pdb interactive debugger.

    Call as '%pdb on', '%pdb 1', '%pdb off' or '%pdb 0'. If called without
    argument it works as a toggle.

    When an exception is triggered, IPython can optionally call the
    interactive pdb debugger after the traceback printout. %pdb toggles
    this feature on and off.

    The initial state of this feature is set in your ipythonrc
    configuration file (the variable is called 'pdb').

    If you want to just activate the debugger AFTER an exception has fired,
    without having to type '%pdb on' and rerunning your code, you can use
    the %debug magic.

%pdef:

    Print the definition header for any callable object.

    If the object is a class, print the constructor information.

%pdoc:

    Print the docstring for an object.

    If the given object is a class, it will print both the class and the
    constructor docstrings.

%pfile:

    Print (or run through pager) the file where an object is defined.

    The file opens at the line where the object definition begins. IPython
    will honor the environment variable PAGER if set, and otherwise will
    do its best to print the file in a convenient form.

    If the given argument is not an object currently defined, IPython will
    try to interpret it as a filename (automatically adding a .py extension
    if needed). You can thus use %pfile as a syntax highlighting code
    viewer.

%pinfo:

    Provide detailed information about an object.

    '%pinfo object' is just a synonym for object? or ?object.

%popd:

    Change to directory popped off the top of the stack.

%profile:

    Print your currently active IPyhton profile.

%prun:

     Run a statement through the python code profiler.

     Usage:\
       %prun [options] statement

     The given statement (which doesn't require quote marks) is run via the
     python profiler in a manner similar to the profile.run() function.
     Namespaces are internally managed to work correctly; profile.run
     cannot be used in IPython because it makes certain assumptions about
     namespaces which do not hold under IPython.

     Options:

     -l <limit>: you can place restrictions on what or how much of the
     profile gets printed. The limit value can be:

       * A string: only information for function names containing this string
       is printed.

       * An integer: only these many lines are printed.

       * A float (between 0 and 1): this fraction of the report is printed
       (for example, use a limit of 0.4 to see the topmost 40% only).

     You can combine several limits with repeated use of the option. For
     example, '-l __init__ -l 5' will print only the topmost 5 lines of
     information about class constructors.

     -r: return the pstats.Stats object generated by the profiling. This
     object has all the information about the profile in it, and you can
     later use it for further analysis or in other functions.

    -s <key>: sort profile by given key. You can provide more than one key
     by using the option several times: '-s key1 -s key2 -s key3...'. The
     default sorting key is 'time'.

     The following is copied verbatim from the profile documentation
     referenced below:

     When more than one key is provided, additional keys are used as
     secondary criteria when the there is equality in all keys selected
     before them.

     Abbreviations can be used for any key names, as long as the
     abbreviation is unambiguous.  The following are the keys currently
     defined:

             Valid Arg       Meaning\
               "calls"      call count\
               "cumulative" cumulative time\
               "file"       file name\
               "module"     file name\
               "pcalls"     primitive call count\
               "line"       line number\
               "name"       function name\
               "nfl"        name/file/line\
               "stdname"    standard name\
               "time"       internal time

     Note that all sorts on statistics are in descending order (placing
     most time consuming items first), where as name, file, and line number
     searches are in ascending order (i.e., alphabetical). The subtle
     distinction between "nfl" and "stdname" is that the standard name is a
     sort of the name as printed, which means that the embedded line
     numbers get compared in an odd way.  For example, lines 3, 20, and 40
     would (if the file names were the same) appear in the string order
     "20" "3" and "40".  In contrast, "nfl" does a numeric compare of the
     line numbers.  In fact, sort_stats("nfl") is the same as
     sort_stats("name", "file", "line").

     -T <filename>: save profile results as shown on screen to a text
     file. The profile is still shown on screen.

     -D <filename>: save (via dump_stats) profile statistics to given
     filename. This data is in a format understod by the pstats module, and
     is generated by a call to the dump_stats() method of profile
     objects. The profile is still shown on screen.

     If you want to run complete programs under the profiler's control, use
     '%run -p [prof_opts] filename.py [args to program]' where prof_opts
     contains profiler specific options as described here.

     You can read the complete documentation for the profile module with:\
       In [1]: import profile; profile.help()

%psearch:

    Search for object in namespaces by wildcard.

    %psearch [options] PATTERN [OBJECT TYPE]

    Note: ? can be used as a synonym for %psearch, at the beginning or at
    the end: both a*? and ?a* are equivalent to '%psearch a*'.  Still, the
    rest of the command line must be unchanged (options come first), so
    for example the following forms are equivalent

    %psearch -i a* function
    -i a* function?
    ?-i a* function

    Arguments:

      PATTERN

      where PATTERN is a string containing * as a wildcard similar to its
      use in a shell.  The pattern is matched in all namespaces on the
      search path. By default objects starting with a single _ are not
      matched, many IPython generated objects have a single
      underscore. The default is case insensitive matching. Matching is
      also done on the attributes of objects and not only on the objects
      in a module.

      [OBJECT TYPE]

      Is the name of a python type from the types module. The name is
      given in lowercase without the ending type, ex. StringType is
      written string. By adding a type here only objects matching the
      given type are matched. Using all here makes the pattern match all
      types (this is the default).

    Options:

      -a: makes the pattern match even objects whose names start with a
      single underscore.  These names are normally ommitted from the
      search.

      -i/-c: make the pattern case insensitive/sensitive.  If neither of
      these options is given, the default is read from your ipythonrc
      file.  The option name which sets this value is
      'wildcards_case_sensitive'.  If this option is not specified in your
      ipythonrc file, IPython's internal default is to do a case sensitive
      search.

      -e/-s NAMESPACE: exclude/search a given namespace.  The pattern you
      specifiy can be searched in any of the following namespaces:
      'builtin', 'user', 'user_global','internal', 'alias', where
      'builtin' and 'user' are the search defaults.  Note that you should
      not use quotes when specifying namespaces.

      'Builtin' contains the python module builtin, 'user' contains all
      user data, 'alias' only contain the shell aliases and no python
      objects, 'internal' contains objects used by IPython.  The
      'user_global' namespace is only used by embedded IPython instances,
      and it contains module-level globals.  You can add namespaces to the
      search with -s or exclude them with -e (these options can be given
      more than once).

    Examples:

    %psearch a*            -> objects beginning with an a
    %psearch -e builtin a* -> objects NOT in the builtin space starting in a
    %psearch a* function   -> all functions beginning with an a
    %psearch re.e*         -> objects beginning with an e in module re
    %psearch r*.e*         -> objects that start with e in modules starting in r
    %psearch r*.* string   -> all strings in modules beginning with r

    Case sensitve search:

    %psearch -c a*         list all object beginning with lower case a

    Show objects beginning with a single _:

    %psearch -a _*         list objects beginning with a single underscore

%psource:

    Print (or run through pager) the source code for an object.

%pushd:

    Place the current dir on stack and change directory.

    Usage:\
      %pushd ['dirname']

%pwd:

    Return the current working directory path.

%pycat:

    Show a syntax-highlighted file through a pager.

    This magic is similar to the cat utility, but it will assume the file
    to be Python source and will show it with syntax highlighting.

%quickref:

    Show a quick reference sheet

%quit:

    Exit IPython, confirming if configured to do so (like %exit)

%r:

    Repeat previous input.

    Note: Consider using the more powerfull %rep instead!

    If given an argument, repeats the previous command which starts with
    the same string, otherwise it just repeats the previous input.

    Shell escaped commands (with ! as first character) are not recognized
    by this system, only pure python code and magic commands.

%rehashdir:

         Add executables in all specified dirs to alias table

    Usage:

    %rehashdir c:/bin;c:/tools
      - Add all executables under c:/bin and c:/tools to alias table, in
      order to make them directly executable from any directory.

      Without arguments, add all executables in current directory.

%rehashx:

    Update the alias table with all executable files in $PATH.

    This version explicitly checks that every entry in $PATH is a file
    with execute access (os.X_OK), so it is much slower than %rehash.

    Under Windows, it checks executability as a match agains a
    '|'-separated string of extensions, stored in the IPython config
    variable win_exec_ext.  This defaults to 'exe|com|bat'.

    This function also resets the root module cache of module completer,
    used on slow filesystems.

%rep:

         Repeat a command, or get command to input line for editing

    - %rep (no arguments):

    Place a string version of last computation result (stored in the special '_'
    variable) to the next input prompt. Allows you to create elaborate command
    lines without using copy-paste::

        $ l = ["hei", "vaan"]
        $ "".join(l)
        ==> heivaan
        $ %rep
        $ heivaan_ <== cursor blinking

    %rep 45

    Place history line 45 to next input prompt. Use %hist to find out the
    number.

    %rep 1-4 6-7 3

    Repeat the specified lines immediately. Input slice syntax is the same as
    in %macro and %save.

    %rep foo

    Place the most recent line that has the substring "foo" to next input.
    (e.g. 'svn ci -m foobar').

%reset:

    Resets the namespace by removing all names defined by the user.

    Input/Output history are left around in case you need them.

%run:

    Run the named file inside IPython as a program.

    Usage:\
      %run [-n -i -t [-N<N>] -d [-b<N>] -p [profile options]] file [args]

    Parameters after the filename are passed as command-line arguments to
    the program (put in sys.argv). Then, control returns to IPython's
    prompt.

    This is similar to running at a system prompt:\
      $ python file args\
    but with the advantage of giving you IPython's tracebacks, and of
    loading all variables into your interactive namespace for further use
    (unless -p is used, see below).

    The file is executed in a namespace initially consisting only of
    __name__=='__main__' and sys.argv constructed as indicated. It thus
    sees its environment as if it were being run as a stand-alone program
    (except for sharing global objects such as previously imported
    modules). But after execution, the IPython interactive namespace gets
    updated with all variables defined in the program (except for __name__
    and sys.argv). This allows for very convenient loading of code for
    interactive work, while giving each program a 'clean sheet' to run in.

    Options:

    -n: __name__ is NOT set to '__main__', but to the running file's name
    without extension (as python does under import).  This allows running
    scripts and reloading the definitions in them without calling code
    protected by an ' if __name__ == "__main__" ' clause.

    -i: run the file in IPython's namespace instead of an empty one. This
    is useful if you are experimenting with code written in a text editor
    which depends on variables defined interactively.

    -e: ignore sys.exit() calls or SystemExit exceptions in the script
    being run.  This is particularly useful if IPython is being used to
    run unittests, which always exit with a sys.exit() call.  In such
    cases you are interested in the output of the test results, not in
    seeing a traceback of the unittest module.

    -t: print timing information at the end of the run.  IPython will give
    you an estimated CPU time consumption for your script, which under
    Unix uses the resource module to avoid the wraparound problems of
    time.clock().  Under Unix, an estimate of time spent on system tasks
    is also given (for Windows platforms this is reported as 0.0).

    If -t is given, an additional -N<N> option can be given, where <N>
    must be an integer indicating how many times you want the script to
    run.  The final timing report will include total and per run results.

    For example (testing the script uniq_stable.py):

        In [1]: run -t uniq_stable

        IPython CPU timings (estimated):\
          User  :    0.19597 s.\
          System:        0.0 s.\

        In [2]: run -t -N5 uniq_stable

        IPython CPU timings (estimated):\
        Total runs performed: 5\
          Times :      Total       Per run\
          User  :   0.910862 s,  0.1821724 s.\
          System:        0.0 s,        0.0 s.

    -d: run your program under the control of pdb, the Python debugger.
    This allows you to execute your program step by step, watch variables,
    etc.  Internally, what IPython does is similar to calling:

      pdb.run('execfile("YOURFILENAME")')

    with a breakpoint set on line 1 of your file.  You can change the line
    number for this automatic breakpoint to be <N> by using the -bN option
    (where N must be an integer).  For example:

      %run -d -b40 myscript

    will set the first breakpoint at line 40 in myscript.py.  Note that
    the first breakpoint must be set on a line which actually does
    something (not a comment or docstring) for it to stop execution.

    When the pdb debugger starts, you will see a (Pdb) prompt.  You must
    first enter 'c' (without qoutes) to start execution up to the first
    breakpoint.

    Entering 'help' gives information about the use of the debugger.  You
    can easily see pdb's full documentation with "import pdb;pdb.help()"
    at a prompt.

    -p: run program under the control of the Python profiler module (which
    prints a detailed report of execution times, function calls, etc).

    You can pass other options after -p which affect the behavior of the
    profiler itself. See the docs for %prun for details.

    In this mode, the program's variables do NOT propagate back to the
    IPython interactive namespace (because they remain in the namespace
    where the profiler executes them).

    Internally this triggers a call to %prun, see its documentation for
    details on the options available specifically for profiling.

    There is one special usage for which the text above doesn't apply:
    if the filename ends with .ipy, the file is run as ipython script,
    just as if the commands were written on IPython prompt.

%runlog:

    Run files as logs.

    Usage:\
      %runlog file1 file2 ...

    Run the named files (treating them as log files) in sequence inside
    the interpreter, and return to the prompt.  This is much slower than
    %run because each line is executed in a try/except block, but it
    allows running files with syntax errors in them.

    Normally IPython will guess when a file is one of its own logfiles, so
    you can typically use %run even for logs. This shorthand allows you to
    force any file to be treated as a log file.

%save:

    Save a set of lines to a given filename.

    Usage:\
      %save [options] filename n1-n2 n3-n4 ... n5 .. n6 ...

    Options:

      -r: use 'raw' input.  By default, the 'processed' history is used,
      so that magics are loaded in their transformed version to valid
      Python.  If this option is given, the raw input as typed as the
      command line is used instead.

    This function uses the same syntax as %macro for line extraction, but
    instead of creating a macro it saves the resulting string to the
    filename you specify.

    It adds a '.py' extension to the file if you don't do so yourself, and
    it asks for confirmation before overwriting existing files.

%sc:

    Shell capture - execute a shell command and capture its output.

    DEPRECATED. Suboptimal, retained for backwards compatibility.

    You should use the form 'var = !command' instead. Example:

     "%sc -l myfiles = ls ~" should now be written as

     "myfiles = !ls ~"

    myfiles.s, myfiles.l and myfiles.n still apply as documented
    below.

    --
    %sc [options] varname=command

    IPython will run the given command using commands.getoutput(), and
    will then update the user's interactive namespace with a variable
    called varname, containing the value of the call.  Your command can
    contain shell wildcards, pipes, etc.

    The '=' sign in the syntax is mandatory, and the variable name you
    supply must follow Python's standard conventions for valid names.

    (A special format without variable name exists for internal use)

    Options:

      -l: list output.  Split the output on newlines into a list before
      assigning it to the given variable.  By default the output is stored
      as a single string.

      -v: verbose.  Print the contents of the variable.

    In most cases you should not need to split as a list, because the
    returned value is a special type of string which can automatically
    provide its contents either as a list (split on newlines) or as a
    space-separated string.  These are convenient, respectively, either
    for sequential processing or to be passed to a shell command.

    For example:

        # Capture into variable a
        In [9]: sc a=ls *py

        # a is a string with embedded newlines
        In [10]: a
        Out[10]: 'setup.py win32_manual_post_install.py'

        # which can be seen as a list:
        In [11]: a.l
        Out[11]: ['setup.py', 'win32_manual_post_install.py']

        # or as a whitespace-separated string:
        In [12]: a.s
        Out[12]: 'setup.py win32_manual_post_install.py'

        # a.s is useful to pass as a single command line:
        In [13]: !wc -l $a.s
          146 setup.py
          130 win32_manual_post_install.py
          276 total

        # while the list form is useful to loop over:
        In [14]: for f in a.l:
           ....:      !wc -l $f
           ....:
        146 setup.py
        130 win32_manual_post_install.py

    Similiarly, the lists returned by the -l option are also special, in
    the sense that you can equally invoke the .s attribute on them to
    automatically get a whitespace-separated string from their contents:

        In [1]: sc -l b=ls *py

        In [2]: b
        Out[2]: ['setup.py', 'win32_manual_post_install.py']

        In [3]: b.s
        Out[3]: 'setup.py win32_manual_post_install.py'

    In summary, both the lists and strings used for ouptut capture have
    the following special attributes:

        .l (or .list) : value as list.
        .n (or .nlstr): value as newline-separated string.
        .s (or .spstr): value as space-separated string.

%store:

        Lightweight persistence for python variables.

    Example:

    ville@badger[~]|1> A = ['hello',10,'world']\
    ville@badger[~]|2> %store A\
    ville@badger[~]|3> Exit

    (IPython session is closed and started again...)

    ville@badger:~$ ipython -p pysh\
    ville@badger[~]|1> print A

    ['hello', 10, 'world']

    Usage:

    %store          - Show list of all variables and their current values\
    %store <var>    - Store the *current* value of the variable to disk\
    %store -d <var> - Remove the variable and its value from storage\
    %store -z       - Remove all variables from storage\
    %store -r       - Refresh all variables from store (delete current vals)\
    %store foo >a.txt  - Store value of foo to new file a.txt\
    %store foo >>a.txt - Append value of foo to file a.txt\

    It should be noted that if you change the value of a variable, you
    need to %store it again if you want to persist the new value.

    Note also that the variables will need to be pickleable; most basic
    python types can be safely %stored.

    Also aliases can be %store'd across sessions.

%sx:

    Shell execute - run a shell command and capture its output.

    %sx command

    IPython will run the given command using commands.getoutput(), and
    return the result formatted as a list (split on '\n').  Since the
    output is _returned_, it will be stored in ipython's regular output
    cache Out[N] and in the '_N' automatic variables.

    Notes:

    1) If an input line begins with '!!', then %sx is automatically
    invoked.  That is, while:
      !ls
    causes ipython to simply issue system('ls'), typing
      !!ls
    is a shorthand equivalent to:
      %sx ls

    2) %sx differs from %sc in that %sx automatically splits into a list,
    like '%sc -l'.  The reason for this is to make it as easy as possible
    to process line-oriented shell output via further python commands.
    %sc is meant to provide much finer control, but requires more
    typing.

    3) Just like %sc -l, this is a list with special attributes:

      .l (or .list) : value as list.
      .n (or .nlstr): value as newline-separated string.
      .s (or .spstr): value as whitespace-separated string.

    This is very useful when trying to use such lists as arguments to
    system commands.

%system_verbose:

    Set verbose printing of system calls.

    If called without an argument, act as a toggle

%time:

    Time execution of a Python statement or expression.

    The CPU and wall clock times are printed, and the value of the
    expression (if any) is returned.  Note that under Win32, system time
    is always reported as 0, since it can not be measured.

    This function provides very basic timing functionality.  In Python
    2.3, the timeit module offers more control and sophistication, so this
    could be rewritten to use it (patches welcome).

    Some examples:

      In [1]: time 2**128
      CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
      Wall time: 0.00
      Out[1]: 340282366920938463463374607431768211456L

      In [2]: n = 1000000

      In [3]: time sum(range(n))
      CPU times: user 1.20 s, sys: 0.05 s, total: 1.25 s
      Wall time: 1.37
      Out[3]: 499999500000L

      In [4]: time print 'hello world'
      hello world
      CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
      Wall time: 0.00

      Note that the time needed by Python to compile the given expression
      will be reported if it is more than 0.1s.  In this example, the
      actual exponentiation is done by Python at compilation time, so while
      the expression can take a noticeable amount of time to compute, that
      time is purely due to the compilation:

      In [5]: time 3**9999;
      CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
      Wall time: 0.00 s

      In [6]: time 3**999999;
      CPU times: user 0.00 s, sys: 0.00 s, total: 0.00 s
      Wall time: 0.00 s
      Compiler : 0.78 s

%timeit:

    Time execution of a Python statement or expression

    Usage:\
      %timeit [-n<N> -r<R> [-t|-c]] statement

    Time execution of a Python statement or expression using the timeit
    module.

    Options:
    -n<N>: execute the given statement <N> times in a loop. If this value
    is not given, a fitting value is chosen.

    -r<R>: repeat the loop iteration <R> times and take the best result.
    Default: 3

    -t: use time.time to measure the time, which is the default on Unix.
    This function measures wall time.

    -c: use time.clock to measure the time, which is the default on
    Windows and measures wall time. On Unix, resource.getrusage is used
    instead and returns the CPU user time.

    -p<P>: use a precision of <P> digits to display the timing result.
    Default: 3

    Examples:\
      In [1]: %timeit pass
      10000000 loops, best of 3: 53.3 ns per loop

      In [2]: u = None

      In [3]: %timeit u is None
      10000000 loops, best of 3: 184 ns per loop

      In [4]: %timeit -r 4 u == None
      1000000 loops, best of 4: 242 ns per loop

      In [5]: import time

      In [6]: %timeit -n1 time.sleep(2)
      1 loops, best of 3: 2 s per loop

    The times reported by %timeit will be slightly higher than those
    reported by the timeit.py script when variables are accessed. This is
    due to the fact that %timeit executes the statement in the namespace
    of the shell, compared with timeit.py, which uses a single setup
    statement to import function or create variables. Generally, the bias
    does not matter as long as results from timeit.py are not mixed with
    those from %timeit.

%unalias:

    Remove an alias

%upgrade:

     Upgrade your IPython installation

    This will copy the config files that don't yet exist in your
    ipython dir from the system config dir. Use this after upgrading
    IPython if you don't wish to delete your .ipython dir.

    Call with -nolegacy to get rid of ipythonrc* files (recommended for
    new users)

%which:

         %which <cmd> => search PATH for files matching cmd. Also scans aliases.

    Traverses PATH and prints all files (not just executables!) that match the
    pattern on command line. Probably more useful in finding stuff
    interactively than 'which', which only prints the first matching item.

    Also discovers and expands aliases, so you'll see what will be executed
    when you call an alias.

    Example:

    [~]|62> %which d
    d -> ls -F --color=auto
      == c:\cygwin\bin\ls.exe
    c:\cygwin\bin\d.exe

    [~]|64> %which diff*
    diff3 -> diff3
      == c:\cygwin\bin\diff3.exe
    diff -> diff
      == c:\cygwin\bin\diff.exe
    c:\cygwin\bin\diff.exe
    c:\cygwin\bin\diff3.exe

%who:

    Print all interactive variables, with some minimal formatting.

    If any arguments are given, only variables whose type matches one of
    these are printed.  For example:

      %who function str

    will only list functions and strings, excluding all other types of
    variables.  To find the proper type names, simply use type(var) at a
    command line to see how python prints type names.  For example:

      In [1]: type('hello')\
      Out[1]: <type 'str'>

    indicates that the type name for strings is 'str'.

    %who always excludes executed names loaded through your configuration
    file and things which are internal to IPython.

    This is deliberate, as typically you may load many modules and the
    purpose of %who is to show you only what you've manually defined.

%who_ls:

    Return a sorted list of all interactive variables.

    If arguments are given, only variables of types matching these
    arguments are returned.

%whos:

    Like %who, but gives some extra information about each variable.

    The same type filtering of %who can be applied here.

    For all variables, the type is printed. Additionally it prints:

      - For {},[],(): their length.

      - For numpy and Numeric arrays, a summary with shape, number of
      elements, typecode and size in memory.

      - Everything else: a string representation, snipping their middle if
      too long.

%xmode:

    Switch modes for the exception handlers.

    Valid modes: Plain, Context and Verbose.

    If called without arguments, acts as a toggle.

### Access to the standard Python help

As of Python 2.1, a help system is available with access to object docstrings and the Python manuals. Simply type ‘help’ (no quotes) to access it. You can also type help(object) to obtain information about a given object, and help(‘keyword’) for information on a keyword. As noted here, you need to properly configure your environment variable PYTHONDOCS for this feature to work correctly.

### Dynamic object information

Typing ?word or word? prints detailed information about an object. If certain strings in the object are too long (docstrings, code, etc.) they get snipped in the center for brevity. This system gives access variable types and values, full source code for any object (if available), function prototypes and other useful information.

Typing ??word or word?? gives access to the full information without snipping long strings. Long strings are sent to the screen through the less pager if longer than the screen and printed otherwise. On systems lacking the less command, IPython uses a very basic internal pager.

The following magic functions are particularly useful for gathering information about your working environment. You can get more details by typing %magic or querying them individually (use %function_name? with or without the %), this is just a summary:

> - %pdoc <object>: Print (or run through a pager if too long) the docstring for an object. If the given object is a class, it will print both the class and the constructor docstrings.
> - %pdef <object>: Print the definition header for any callable object. If the object is a class, print the constructor information.
> - %psource <object>: Print (or run through a pager if too long) the source code for an object.
> - %pfile <object>: Show the entire source file where an object was defined via a pager, opening it at the line where the object definition begins.
> - %who/%whos: These functions give information about identifiers you have defined interactively (not things you loaded or defined in your configuration files). %who just prints a list of identifiers and %whos prints a table with some basic details about each identifier.

Note that the dynamic object information functions (?/??, %pdoc, %pfile, %pdef, %psource) give you access to documentation even on things which are not really defined as separate identifiers. Try for example typing {}.get? or after doing import os, type os.path.abspath??.

### Readline-based features

These features require the GNU readline library, so they won’t work if your Python installation lacks readline support. We will first describe the default behavior IPython uses, and then how to change it to suit your preferences.

#### Command line completion

At any time, hitting TAB will complete any available python commands or variable names, and show you a list of the possible completions if there’s no unambiguous one. It will also complete filenames in the current directory if no python names match what you’ve typed so far.

#### Search command history

IPython provides two ways for searching through previous input and thus reduce the need for repetitive typing:

> 1. Start typing, and then use Ctrl-p (previous,up) and Ctrl-n (next,down) to search through only the history items that match what you’ve typed so far. If you use Ctrl-p/Ctrl-n at a blank prompt, they just behave like normal arrow keys.
> 2. Hit Ctrl-r: opens a search prompt. Begin typing and the system searches your history for lines that contain what you’ve typed so far, completing as much as it can.

#### Persistent command history across sessions

IPython will save your input history when it leaves and reload it next time you restart it. By default, the history file is named $IPYTHONDIR/history, but if you’ve loaded a named profile, ‘-PROFILE_NAME’ is appended to the name. This allows you to keep separate histories related to various tasks: commands related to numerical work will not be clobbered by a system shell history, for example.

#### Autoindent

IPython can recognize lines ending in ‘:’ and indent the next line, while also un-indenting automatically after ‘raise’ or ‘return’.

This feature uses the readline library, so it will honor your ~/.inputrc configuration (or whatever file your INPUTRC variable points to). Adding the following lines to your .inputrc file can make indenting/unindenting more convenient (M-i indents, M-u unindents):

    $if Python
    "\M-i": "    "
    "\M-u": "\d\d\d\d"
    $endif

Note that there are 4 spaces between the quote marks after “M-i” above.

Warning: this feature is ON by default, but it can cause problems with the pasting of multi-line indented code (the pasted code gets re-indented on each line). A magic function %autoindent allows you to toggle it on/off at runtime. You can also disable it permanently on in your ipythonrc file (set autoindent 0).

#### Customizing readline behavior

All these features are based on the GNU readline library, which has an extremely customizable interface. Normally, readline is configured via a file which defines the behavior of the library; the details of the syntax for this can be found in the readline documentation available with your system or on the Internet. IPython doesn’t read this file (if it exists) directly, but it does support passing to readline valid options via a simple interface. In brief, you can customize readline by setting the following options in your ipythonrc configuration file (note that these options can not be specified at the command line):

> - readline_parse_and_bind: this option can appear as many times as you want, each time defining a string to be executed via a readline.parse_and_bind() command. The syntax for valid commands of this kind can be found by reading the documentation for the GNU readline library, as these commands are of the kind which readline accepts in its configuration file.

> - readline_remove_delims: a string of characters to be removed from the default word-delimiters list used by readline, so that completions may be performed on strings which contain them. Do not change the default value unless you know what you’re doing.

> - readline_omit__names: when tab-completion is enabled, hitting <tab> after a ‘.’ in a name will complete all attributes of an object, including all the special methods whose names include double underscores (like __getitem__ or __class__). If you’d rather not see these names by default, you can set this option to 1. Note that even when this option is set, you can still see those names by explicitly typing a _ after the period and hitting <tab>: ‘name._<tab>’ will always complete attribute names starting with ‘_’.

>   This option is off by default so that new users see all attributes of any objects they are dealing with.

You will find the default values along with a corresponding detailed explanation in your ipythonrc file.

### Session logging and restoring

You can log all input from a session either by starting IPython with the command line switches -log or -logfile (see here) or by activating the logging at any moment with the magic function %logstart.

Log files can later be reloaded with the -logplay option and IPython will attempt to ‘replay’ the log by executing all the lines in it, thus restoring the state of a previous session. This feature is not quite perfect, but can still be useful in many cases.

The log files can also be used as a way to have a permanent record of any code you wrote while experimenting. Log files are regular text files which you can later open in your favorite text editor to extract code or to ‘clean them up’ before using them to replay a session.

The %logstart function for activating logging in mid-session is used as follows:

%logstart [log_name [log_mode]]

If no name is given, it defaults to a file named ‘log’ in your IPYTHONDIR directory, in ‘rotate’ mode (see below).

‘%logstart name’ saves to file ‘name’ in ‘backup’ mode. It saves your history up to that point and then continues logging.

%logstart takes a second optional parameter: logging mode. This can be one of (note that the modes are given unquoted):

> - [over:] overwrite existing log_name.
> - [backup:] rename (if exists) to log_name~ and start log_name.
> - [append:] well, that says it.
> - [rotate:] create rotating logs log_name.1~, log_name.2~, etc.

The %logoff and %logon functions allow you to temporarily stop and resume logging to a file which had previously been started with %logstart. They will fail (with an explanation) if you try to use them before logging has been started.

### System shell access

Any input line beginning with a ! character is passed verbatim (minus the !, of course) to the underlying operating system. For example, typing !ls will run ‘ls’ in the current directory.

### Manual capture of command output

If the input line begins with two exclamation marks, !!, the command is executed but its output is captured and returned as a python list, split on newlines. Any output sent by the subprocess to standard error is printed separately, so that the resulting list only captures standard output. The !! syntax is a shorthand for the %sx magic command.

Finally, the %sc magic (short for ‘shell capture’) is similar to %sx, but allowing more fine-grained control of the capture details, and storing the result directly into a named variable. The direct use of %sc is now deprecated, and you should ise the `var = !cmd` syntax instead.

IPython also allows you to expand the value of python variables when making system calls. Any python variable or expression which you prepend with $ will get expanded before the system call is made:

    In [1]: pyvar='Hello world'
    In [2]: !echo "A python variable: $pyvar"
    A python variable: Hello world

If you want the shell to actually see a literal $, you need to type it twice:

    In [3]: !echo "A system variable: $$HOME"
    A system variable: /home/fperez

You can pass arbitrary expressions, though you’ll need to delimit them with {} if there is ambiguity as to the extent of the expression:

    In [5]: x=10
    In [6]: y=20
    In [13]: !echo $x+y
    10+y
    In [7]: !echo ${x+y}
    30

Even object attributes can be expanded:

    In [12]: !echo $sys.argv
    [/home/fperez/usr/bin/ipython]

### System command aliases

The %alias magic function and the alias option in the ipythonrc configuration file allow you to define magic functions which are in fact system shell commands. These aliases can have parameters.

‘%alias alias_name cmd’ defines ‘alias_name’ as an alias for ‘cmd’

Then, typing ‘%alias_name params’ will execute the system command ‘cmd params’ (from your underlying operating system).

You can also define aliases with parameters using %s specifiers (one per parameter). The following example defines the %parts function as an alias to the command ‘echo first %s second %s’ where each %s will be replaced by a positional parameter to the call to %parts:

    In [1]: alias parts echo first %s second %s
    In [2]: %parts A B
    first A second B
    In [3]: %parts A
    Incorrect number of arguments: 2 expected.
    parts is an alias to: 'echo first %s second %s'

If called with no parameters, %alias prints the table of currently defined aliases.

The %rehash/rehashx magics allow you to load your entire $PATH as ipython aliases. See their respective docstrings (or sec. 6.2 <#sec:magic> for further details).

### Recursive reload

The dreload function does a recursive reload of a module: changes made to the module since you imported will actually be available without having to exit.

### Verbose and colored exception traceback printouts

IPython provides the option to see very detailed exception tracebacks, which can be especially useful when debugging large programs. You can run any Python file with the %run function to benefit from these detailed tracebacks. Furthermore, both normal and verbose tracebacks can be colored (if your terminal supports it) which makes them much easier to parse visually.

See the magic xmode and colors functions for details (just type %magic).

These features are basically a terminal version of Ka-Ping Yee’s cgitb module, now part of the standard Python library.

### Input caching system

IPython offers numbered prompts (In/Out) with input and output caching. All input is saved and can be retrieved as variables (besides the usual arrow key recall).

The following GLOBAL variables always exist (so don’t overwrite them!): _i: stores previous input. _ii: next previous. _iii: next-next previous. _ih : a list of all input _ih[n] is the input from line n and this list is aliased to the global variable In. If you overwrite In with a variable of your own, you can remake the assignment to the internal list with a simple ‘In=_ih’.

Additionally, global variables named _i<n> are dynamically created (<n> being the prompt counter), such that _i<n> == _ih[<n>] == In[<n>].

For example, what you typed at prompt 14 is available as _i14, _ih[14] and In[14].

This allows you to easily cut and paste multi line interactive prompts by printing them out: they print like a clean string, without prompt characters. You can also manipulate them like regular variables (they are strings), modify or exec them (typing ‘exec _i9’ will re-execute the contents of input prompt 9, ‘exec In[9:14]+In[18]’ will re-execute lines 9 through 13 and line 18).

You can also re-execute multiple lines of input easily by using the magic %macro function (which automates the process and allows re-execution without having to type ‘exec’ every time). The macro system also allows you to re-execute previous lines which include magic function calls (which require special processing). Type %macro? or see sec. 6.2 <#sec:magic> for more details on the macro system.

A history function %hist allows you to see any part of your input history by printing a range of the _i variables.

### Output caching system

For output that is returned from actions, a system similar to the input cache exists but using _ instead of _i. Only actions that produce a result (NOT assignments, for example) are cached. If you are familiar with Mathematica, IPython’s _ variables behave exactly like Mathematica’s % variables.

The following GLOBAL variables always exist (so don’t overwrite them!):

> - [_] (a single underscore) : stores previous output, like Python’s default interpreter.
> - [__] (two underscores): next previous.
> - [___] (three underscores): next-next previous.

Additionally, global variables named _<n> are dynamically created (<n> being the prompt counter), such that the result of output <n> is always available as _<n> (don’t use the angle brackets, just the number, e.g. _21).

These global variables are all stored in a global dictionary (not a list, since it only has entries for lines which returned a result) available under the names _oh and Out (similar to _ih and In). So the output from line 12 can be obtained as _12, Out[12] or _oh[12]. If you accidentally overwrite the Out variable you can recover it by typing ‘Out=_oh’ at the prompt.

This system obviously can potentially put heavy memory demands on your system, since it prevents Python’s garbage collector from removing any previously computed results. You can control how many results are kept in memory with the option (at the command line or in your ipythonrc file) cache_size. If you set it to 0, the whole system is completely disabled and the prompts revert to the classic ‘>>>’ of normal Python.

### Directory history

Your history of visited directories is kept in the global list _dh, and the magic %cd command can be used to go to any entry in that list. The %dhist command allows you to view this history. do `cd -<TAB` to conventiently view the directory history.

### Automatic parentheses and quotes

These features were adapted from Nathan Gray’s LazyPython. They are meant to allow less typing for common situations.

### Automatic parentheses

Callable objects (i.e. functions, methods, etc) can be invoked like this (notice the commas between the arguments):

    >>> callable_ob arg1, arg2, arg3

and the input will be translated to this:

    -> callable_ob(arg1, arg2, arg3)

You can force automatic parentheses by using ‘/’ as the first character of a line. For example:

    >>> /globals # becomes 'globals()'

Note that the ‘/’ MUST be the first character on the line! This won’t work:

    >>> print /globals # syntax error

In most cases the automatic algorithm should work, so you should rarely need to explicitly invoke /. One notable exception is if you are trying to call a function with a list of tuples as arguments (the parenthesis will confuse IPython):

    In [1]: zip (1,2,3),(4,5,6) # won't work

but this will work:

    In [2]: /zip (1,2,3),(4,5,6)
    ---> zip ((1,2,3),(4,5,6))
    Out[2]= [(1, 4), (2, 5), (3, 6)]

IPython tells you that it has altered your command line by displaying the new command line preceded by ->. e.g.:

    In [18]: callable list
    ----> callable (list)

### Automatic quoting

You can force automatic quoting of a function’s arguments by using ‘,’ or ‘;’ as the first character of a line. For example:

    >>> ,my_function /home/me # becomes my_function("/home/me")

If you use ‘;’ instead, the whole argument is quoted as a single string (while ‘,’ splits on whitespace):

    >>> ,my_function a b c # becomes my_function("a","b","c")

    >>> ;my_function a b c # becomes my_function("a b c")

Note that the ‘,’ or ‘;’ MUST be the first character on the line! This won’t work:

    >>> x = ,my_function /home/me # syntax error

## IPython as your default Python environment

Python honors the environment variable PYTHONSTARTUP and will execute at startup the file referenced by this variable. If you put at the end of this file the following two lines of code:

    import IPython
    IPython.Shell.IPShell().mainloop(sys_exit=1)

then IPython will be your working environment anytime you start Python. The sys_exit=1 is needed to have IPython issue a call to sys.exit() when it finishes, otherwise you’ll be back at the normal Python ‘>>>’ prompt.

This is probably useful to developers who manage multiple Python versions and don’t want to have correspondingly multiple IPython versions. Note that in this mode, there is no way to pass IPython any command-line options, as those are trapped first by Python itself.

## Embedding IPython

It is possible to start an IPython instance inside your own Python programs. This allows you to evaluate dynamically the state of your code, operate with your variables, analyze them, etc. Note however that any changes you make to values while in the shell do not propagate back to the running code, so it is safe to modify your values because you won’t break your code in bizarre ways by doing so.

This feature allows you to easily have a fully functional python environment for doing object introspection anywhere in your code with a simple function call. In some cases a simple print statement is enough, but if you need to do more detailed analysis of a code fragment this feature can be very valuable.

It can also be useful in scientific computing situations where it is common to need to do some automatic, computationally intensive part and then stop to look at data, plots, etc. Opening an IPython instance will give you full access to your data and functions, and you can resume program execution once you are done with the interactive part (perhaps to stop again later, as many times as needed).

The following code snippet is the bare minimum you need to include in your Python programs for this to work (detailed examples follow later):

    from IPython.Shell import IPShellEmbed

    ipshell = IPShellEmbed()

    ipshell() # this call anywhere in your program will start IPython

You can run embedded instances even in code which is itself being run at the IPython interactive prompt with ‘%run <filename>’. Since it’s easy to get lost as to where you are (in your top-level IPython or in your embedded one), it’s a good idea in such cases to set the in/out prompts to something different for the embedded instances. The code examples below illustrate this.

You can also have multiple IPython instances in your program and open them separately, for example with different options for data presentation. If you close and open the same instance multiple times, its prompt counters simply continue from each execution to the next.

Please look at the docstrings in the Shell.py module for more details on the use of this system.

The following sample file illustrating how to use the embedding functionality is provided in the examples directory as example-embed.py. It should be fairly self-explanatory:

    #!/usr/bin/env python

    """An example of how to embed an IPython shell into a running program.

    Please see the documentation in the IPython.Shell module for more details.

    The accompanying file example-embed-short.py has quick code fragments for
    embedding which you can cut and paste in your code once you understand how
    things work.

    The code in this file is deliberately extra-verbose, meant for learning."""

    # The basics to get you going:

    # IPython sets the __IPYTHON__ variable so you can know if you have nested
    # copies running.

    # Try running this code both at the command line and from inside IPython (with
    # %run example-embed.py)
    try:
        __IPYTHON__
    except NameError:
        nested = 0
        args = ['']
    else:
        print "Running nested copies of IPython."
        print "The prompts for the nested copy have been modified"
        nested = 1
        # what the embedded instance will see as sys.argv:
        args = ['-pi1','In <\\#>: ','-pi2','   .\\D.: ',
                '-po','Out<\\#>: ','-nosep']

    # First import the embeddable shell class
    from IPython.Shell import IPShellEmbed

    # Now create an instance of the embeddable shell. The first argument is a
    # string with options exactly as you would type them if you were starting
    # IPython at the system command line. Any parameters you want to define for
    # configuration can thus be specified here.
    ipshell = IPShellEmbed(args,
                           banner = 'Dropping into IPython',
                           exit_msg = 'Leaving Interpreter, back to program.')

    # Make a second instance, you can have as many as you want.
    if nested:
        args[1] = 'In2<\\#>'
    else:
        args = ['-pi1','In2<\\#>: ','-pi2','   .\\D.: ',
                '-po','Out<\\#>: ','-nosep']
    ipshell2 = IPShellEmbed(args,banner = 'Second IPython instance.')

    print '\nHello. This is printed from the main controller program.\n'

    # You can then call ipshell() anywhere you need it (with an optional
    # message):
    ipshell('***Called from top level. '
            'Hit Ctrl-D to exit interpreter and continue program.\n'
            'Note that if you use %kill_embedded, you can fully deactivate\n'
            'This embedded instance so it will never turn on again')

    print '\nBack in caller program, moving along...\n'

    #---------------------------------------------------------------------------
    # More details:

    # IPShellEmbed instances don't print the standard system banner and
    # messages. The IPython banner (which actually may contain initialization
    # messages) is available as <instance>.IP.BANNER in case you want it.

    # IPShellEmbed instances print the following information everytime they
    # start:

    # - A global startup banner.

    # - A call-specific header string, which you can use to indicate where in the
    # execution flow the shell is starting.

    # They also print an exit message every time they exit.

    # Both the startup banner and the exit message default to None, and can be set
    # either at the instance constructor or at any other time with the
    # set_banner() and set_exit_msg() methods.

    # The shell instance can be also put in 'dummy' mode globally or on a per-call
    # basis. This gives you fine control for debugging without having to change
    # code all over the place.

    # The code below illustrates all this.

    # This is how the global banner and exit_msg can be reset at any point
    ipshell.set_banner('Entering interpreter - New Banner')
    ipshell.set_exit_msg('Leaving interpreter - New exit_msg')

    def foo(m):
        s = 'spam'
        ipshell('***In foo(). Try @whos, or print s or m:')
        print 'foo says m = ',m

    def bar(n):
        s = 'eggs'
        ipshell('***In bar(). Try @whos, or print s or n:')
        print 'bar says n = ',n

    # Some calls to the above functions which will trigger IPython:
    print 'Main program calling foo("eggs")\n'
    foo('eggs')

    # The shell can be put in 'dummy' mode where calls to it silently return. This
    # allows you, for example, to globally turn off debugging for a program with a
    # single call.
    ipshell.set_dummy_mode(1)
    print '\nTrying to call IPython which is now "dummy":'
    ipshell()
    print 'Nothing happened...'
    # The global 'dummy' mode can still be overridden for a single call
    print '\nOverriding dummy mode manually:'
    ipshell(dummy=0)

    # Reactivate the IPython shell
    ipshell.set_dummy_mode(0)

    print 'You can even have multiple embedded instances:'
    ipshell2()

    print '\nMain program calling bar("spam")\n'
    bar('spam')

    print 'Main program finished. Bye!'

    #********************** End of file <example-embed.py> ***********************

Once you understand how the system functions, you can use the following code fragments in your programs which are ready for cut and paste:

    """Quick code snippets for embedding IPython into other programs.

    See example-embed.py for full details, this file has the bare minimum code for
    cut and paste use once you understand how to use the system."""

    #---------------------------------------------------------------------------
    # This code loads IPython but modifies a few things if it detects it's running
    # embedded in another IPython session (helps avoid confusion)

    try:
        __IPYTHON__
    except NameError:
        argv = ['']
        banner = exit_msg = ''
    else:
        # Command-line options for IPython (a list like sys.argv)
        argv = ['-pi1','In <\\#>:','-pi2','   .\\D.:','-po','Out<\\#>:']
        banner = '*** Nested interpreter ***'
        exit_msg = '*** Back in main IPython ***'

    # First import the embeddable shell class
    from IPython.Shell import IPShellEmbed
    # Now create the IPython shell instance. Put ipshell() anywhere in your code
    # where you want it to open.
    ipshell = IPShellEmbed(argv,banner=banner,exit_msg=exit_msg)

    #---------------------------------------------------------------------------
    # This code will load an embeddable IPython shell always with no changes for
    # nested embededings.

    from IPython.Shell import IPShellEmbed
    ipshell = IPShellEmbed()
    # Now ipshell() will open IPython anywhere in the code.

    #---------------------------------------------------------------------------
    # This code loads an embeddable shell only if NOT running inside
    # IPython. Inside IPython, the embeddable shell variable ipshell is just a
    # dummy function.

    try:
        __IPYTHON__
    except NameError:
        from IPython.Shell import IPShellEmbed
        ipshell = IPShellEmbed()
        # Now ipshell() will open IPython anywhere in the code
    else:
        # Define a dummy ipshell() so the same code doesn't crash inside an
        # interactive IPython
        def ipshell(): pass

    #******************* End of file <example-embed-short.py> ********************

## Using the Python debugger (pdb)

### Running entire programs via pdb

pdb, the Python debugger, is a powerful interactive debugger which allows you to step through code, set breakpoints, watch variables, etc. IPython makes it very easy to start any script under the control of pdb, regardless of whether you have wrapped it into a ‘main()’ function or not. For this, simply type ‘%run -d myscript’ at an IPython prompt. See the %run command’s documentation (via ‘%run?’ or in Sec. magic for more details, including how to control where pdb will stop execution first.

For more information on the use of the pdb debugger, read the included pdb.doc file (part of the standard Python distribution). On a stock Linux system it is located at /usr/lib/python2.3/pdb.doc, but the easiest way to read it is by using the help() function of the pdb module as follows (in an IPython prompt):

In [1]: import pdb In [2]: pdb.help()

This will load the pdb.doc document in a file viewer for you automatically.

### Automatic invocation of pdb on exceptions

IPython, if started with the -pdb option (or if the option is set in your rc file) can call the Python pdb debugger every time your code triggers an uncaught exception. This feature can also be toggled at any time with the %pdb magic command. This can be extremely useful in order to find the origin of subtle bugs, because pdb opens up at the point in your code which triggered the exception, and while your program is at this point ‘dead’, all the data is still available and you can walk up and down the stack frame and understand the origin of the problem.

Furthermore, you can use these debugging facilities both with the embedded IPython mode and without IPython at all. For an embedded shell (see sec. Embedding), simply call the constructor with ‘-pdb’ in the argument string and automatically pdb will be called if an uncaught exception is triggered by your code.

For stand-alone use of the feature in your programs which do not use IPython at all, put the following lines toward the top of your ‘main’ routine:

    import sys,IPython.ultraTB
    sys.excepthook = IPython.ultraTB.FormattedTB(mode='Verbose',
    color_scheme='Linux', call_pdb=1)

The mode keyword can be either ‘Verbose’ or ‘Plain’, giving either very detailed or normal tracebacks respectively. The color_scheme keyword can be one of ‘NoColor’, ‘Linux’ (default) or ‘LightBG’. These are the same options which can be set in IPython with -colors and -xmode.

This will give any of your programs detailed, colored tracebacks with automatic invocation of pdb.

## Extensions for syntax processing

This isn’t for the faint of heart, because the potential for breaking things is quite high. But it can be a very powerful and useful feature. In a nutshell, you can redefine the way IPython processes the user input line to accept new, special extensions to the syntax without needing to change any of IPython’s own code.

In the IPython/Extensions directory you will find some examples supplied, which we will briefly describe now. These can be used ‘as is’ (and both provide very useful functionality), or you can use them as a starting point for writing your own extensions.

### Pasting of code starting with ‘>>> ‘ or ‘... ‘

In the python tutorial it is common to find code examples which have been taken from real python sessions. The problem with those is that all the lines begin with either ‘>>> ‘ or ‘... ‘, which makes it impossible to paste them all at once. One must instead do a line by line manual copying, carefully removing the leading extraneous characters.

This extension identifies those starting characters and removes them from the input automatically, so that one can paste multi-line examples directly into IPython, saving a lot of time. Please look at the file InterpreterPasteInput.py in the IPython/Extensions directory for details on how this is done.

IPython comes with a special profile enabling this feature, called tutorial. Simply start IPython via ‘ipython -p tutorial’ and the feature will be available. In a normal IPython session you can activate the feature by importing the corresponding module with: In [1]: import IPython.Extensions.InterpreterPasteInput

The following is a ‘screenshot’ of how things work when this extension is on, copying an example from the standard tutorial:

    IPython profile: tutorial

    *** Pasting of code with ">>>" or "..." has been enabled.

    In [1]: >>> def fib2(n): # return Fibonacci series up to n
       ...: ...     """Return a list containing the Fibonacci series up to
    n."""
       ...: ...     result = []
       ...: ...     a, b = 0, 1
       ...: ...     while b < n:
       ...: ...         result.append(b)    # see below
       ...: ...         a, b = b, a+b
       ...: ...     return result
       ...:

    In [2]: fib2(10)
    Out[2]: [1, 1, 2, 3, 5, 8]

Note that as currently written, this extension does not recognize IPython’s prompts for pasting. Those are more complicated, since the user can change them very easily, they involve numbers and can vary in length. One could however extract all the relevant information from the IPython instance and build an appropriate regular expression. This is left as an exercise for the reader.

### Input of physical quantities with units

The module PhysicalQInput allows a simplified form of input for physical quantities with units. This file is meant to be used in conjunction with the PhysicalQInteractive module (in the same directory) and Physics.PhysicalQuantities from Konrad Hinsen’s ScientificPython (http://dirac.cnrs-orleans.fr/ScientificPython/).

The Physics.PhysicalQuantities module defines PhysicalQuantity objects, but these must be declared as instances of a class. For example, to define v as a velocity of 3 m/s, normally you would write:

    In [1]: v = PhysicalQuantity(3,'m/s')

Using the PhysicalQ_Input extension this can be input instead as: In [1]: v = 3 m/s which is much more convenient for interactive use (even though it is blatantly invalid Python syntax).

The physics profile supplied with IPython (enabled via ‘ipython -p physics’) uses these extensions, which you can also activate with:

from math import * # math MUST be imported BEFORE PhysicalQInteractive from IPython.Extensions.PhysicalQInteractive import * import IPython.Extensions.PhysicalQInput

## Threading support

WARNING: The threading support is still somewhat experimental, and it has only seen reasonable testing under Linux. Threaded code is particularly tricky to debug, and it tends to show extremely platform-dependent behavior. Since I only have access to Linux machines, I will have to rely on user’s experiences and assistance for this area of IPython to improve under other platforms.

IPython, via the -gthread , -qthread, -q4thread and -wthread options (described in Sec. Threading options), can run in multithreaded mode to support pyGTK, Qt3, Qt4 and WXPython applications respectively. These GUI toolkits need to control the python main loop of execution, so under a normal Python interpreter, starting a pyGTK, Qt3, Qt4 or WXPython application will immediately freeze the shell.

IPython, with one of these options (you can only use one at a time), separates the graphical loop and IPython’s code execution run into different threads. This allows you to test interactively (with %run, for example) your GUI code without blocking.

A nice mini-tutorial on using IPython along with the Qt Designer application is available at the SciPy wiki: http://www.scipy.org/Cookbook/Matplotlib/Qt_with_IPython_and_Designer.

### Tk issues

As indicated in Sec. Threading options, a special -tk option is provided to try and allow Tk graphical applications to coexist interactively with WX, Qt or GTK ones. Whether this works at all, however, is very platform and configuration dependent. Please experiment with simple test cases before committing to using this combination of Tk and GTK/Qt/WX threading in a production environment.

### I/O pitfalls

Be mindful that the Python interpreter switches between threads every $N$ bytecodes, where the default value as of Python 2.3 is $N=100.$ This value can be read by using the sys.getcheckinterval() function, and it can be reset via sys.setcheckinterval(N). This switching of threads can cause subtly confusing effects if one of your threads is doing file I/O. In text mode, most systems only flush file buffers when they encounter a ‘n’. An instruction as simple as:

    print >> filehandle, ''hello world''

actually consists of several bytecodes, so it is possible that the newline does not reach your file before the next thread switch. Similarly, if you are writing to a file in binary mode, the file won’t be flushed until the buffer fills, and your other thread may see apparently truncated files.

For this reason, if you are using IPython’s thread support and have (for example) a GUI application which will read data generated by files written to from the IPython thread, the safest approach is to open all of your files in unbuffered mode (the third argument to the file/open function is the buffering value):

    filehandle = open(filename,mode,0)

This is obviously a brute force way of avoiding race conditions with the file buffering. If you want to do it cleanly, and you have a resource which is being shared by the interactive IPython loop and your GUI thread, you should really handle it with thread locking and syncrhonization properties. The Python documentation discusses these.

## Interactive demos with IPython

IPython ships with a basic system for running scripts interactively in sections, useful when presenting code to audiences. A few tags embedded in comments (so that the script remains valid Python code) divide a file into separate blocks, and the demo can be run one block at a time, with IPython printing (with syntax highlighting) the block before executing it, and returning to the interactive prompt after each block. The interactive namespace is updated after each block is run with the contents of the demo’s namespace.

This allows you to show a piece of code, run it and then execute interactively commands based on the variables just created. Once you want to continue, you simply execute the next block of the demo. The following listing shows the markup necessary for dividing a script into sections for execution as a demo:

    """A simple interactive demo to illustrate the use of IPython's Demo class.

    Any python script can be run as a demo, but that does little more than showing
    it on-screen, syntax-highlighted in one shot.  If you add a little simple
    markup, you can stop at specified intervals and return to the ipython prompt,
    resuming execution later.
    """

    print 'Hello, welcome to an interactive IPython demo.'
    print 'Executing this block should require confirmation before proceeding,'
    print 'unless auto_all has been set to true in the demo object'

    # The mark below defines a block boundary, which is a point where IPython will
    # stop execution and return to the interactive prompt.
    # Note that in actual interactive execution,
    # <demo> --- stop ---

    x = 1
    y = 2

    # <demo> --- stop ---

    # the mark below makes this block as silent
    # <demo> silent

    print 'This is a silent block, which gets executed but not printed.'

    # <demo> --- stop ---
    # <demo> auto
    print 'This is an automatic block.'
    print 'It is executed without asking for confirmation, but printed.'
    z = x+y

    print 'z=',x

    # <demo> --- stop ---
    # This is just another normal block.
    print 'z is now:', z

    print 'bye!'

In order to run a file as a demo, you must first make a Demo object out of it. If the file is named myscript.py, the following code will make a demo:

    from IPython.demo import Demo

    mydemo = Demo('myscript.py')

This creates the mydemo object, whose blocks you run one at a time by simply calling the object with no arguments. If you have autocall active in IPython (the default), all you need to do is type:

    mydemo

and IPython will call it, executing each block. Demo objects can be restarted, you can move forward or back skipping blocks, re-execute the last block, etc. Simply use the Tab key on a demo object to see its methods, and call ‘?’ on them to see their docstrings for more usage details. In addition, the demo module itself contains a comprehensive docstring, which you can access via:

    from IPython import demo

    demo?

Limitations: It is important to note that these demos are limited to fairly simple uses. In particular, you can not put division marks in indented code (loops, if statements, function definitions, etc.) Supporting something like this would basically require tracking the internal execution state of the Python interpreter, so only top-level divisions are allowed. If you want to be able to open an IPython instance at an arbitrary point in a program, you can use IPython’s embedding facilities, described in detail in Sec. 9

## Plotting with matplotlib

The matplotlib library (http://matplotlib.sourceforge.net http://matplotlib.sourceforge.net) provides high quality 2D plotting for Python. Matplotlib can produce plots on screen using a variety of GUI toolkits, including Tk, GTK and WXPython. It also provides a number of commands useful for scientific computing, all with a syntax compatible with that of the popular Matlab program.

IPython accepts the special option -pylab (see here). This configures it to support matplotlib, honoring the settings in the .matplotlibrc file. IPython will detect the user’s choice of matplotlib GUI backend, and automatically select the proper threading model to prevent blocking. It also sets matplotlib in interactive mode and modifies %run slightly, so that any matplotlib-based script can be executed using %run and the final show() command does not block the interactive shell.

The -pylab option must be given first in order for IPython to configure its threading mode. However, you can still issue other options afterwards. This allows you to have a matplotlib-based environment customized with additional modules using the standard IPython profile mechanism (see here): `ipython -pylab -p myprofile` will load the profile defined in ipythonrc-myprofile after configuring matplotlib.

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