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# config.application

## Module: `config.application`

Inheritance diagram for `IPython.config.application`:

A base class for a configurable application.

Authors:

- Brian Granger
- Min RK

## Classes

### `Application`

class `IPython.config.application.``Application`(**kwargs)

  Bases: `IPython.config.configurable.SingletonConfigurable`

  A singleton application with full configuration support.

  `__init__`(**kwargs)
  `aliases`

    An instance of a Python dict.

  classmethod `class_config_section`()

    Get the config class config section

  classmethod `class_get_help`()

    Get the help string for this class in ReST format.

  classmethod `class_get_trait_help`(trait)

    Get the help string for a single trait.

  classmethod `class_print_help`()

    Get the help string for a single trait and print it.

  classmethod `class_trait_names`(**metadata)

    Get a list of all the names of this classes traits.

    This method is just like the `trait_names()` method, but is unbound.

  classmethod `class_traits`(**metadata)

    Get a list of all the traits of this class.

    This method is just like the `traits()` method, but is unbound.

    The TraitTypes returned don’t know anything about the values that the various HasTrait’s instances are holding.

    This follows the same algorithm as traits does and does not allow for any simple way of specifying merely that a metadata name exists, but has any value. This is because get_metadata returns None if a metadata key doesn’t exist.

  `classes`

    An instance of a Python list.

  classmethod `clear_instance`()

    unset _instance for this class and singleton parents.

  `config`

    A trait whose value must be an instance of a specified class.

    The value can also be an instance of a subclass of the specified class.

  `created` = None
  `description`

    A trait for unicode strings.

  `examples`

    A trait for unicode strings.

  `exit`(exit_status=0)
  `extra_args`

    An instance of a Python list.

  `flags`

    An instance of a Python dict.

  `generate_config_file`()

    generate default config file from Configurables

  `init_logging`()

    Start logging for this application.

    The default is to log to stdout using a StreaHandler. The log level starts at loggin.WARN, but this can be adjusted by setting the `log_level` attribute.

  `initialize`(argv=None)

    Do the basic steps to configure me.

    Override in subclasses.

  `initialize_subcommand`(subc, argv=None)

    Initialize a subcommand with argv.

  classmethod `initialized`()

    Has an instance been created?

  classmethod `instance`(*args, **kwargs)

    Returns a global instance of this class.

    This method create a new instance if none have previously been created and returns a previously created instance is one already exists.

    The arguments and keyword arguments passed to this method are passed on to the `__init__()` method of the class upon instantiation.

    Examples

    Create a singleton class using instance, and retrieve it:

        >>> from IPython.config.configurable import SingletonConfigurable
        >>> class Foo(SingletonConfigurable): pass
        >>> foo = Foo.instance()
        >>> foo == Foo.instance()
        True

    Create a subclass that is retrived using the base class instance:

        >>> class Bar(SingletonConfigurable): pass
        >>> class Bam(Bar): pass
        >>> bam = Bam.instance()
        >>> bam == Bar.instance()
        True

  `keyvalue_description`

    A trait for unicode strings.

  `load_config_file`(filename, path=None)

    Load a .py based config file by filename and path.

  `log_level`

    An enum that whose value must be in a given sequence.

  `name`

    A trait for unicode strings.

  `on_trait_change`(handler, name=None, remove=False)

    Setup a handler to be called when a trait changes.

    This is used to setup dynamic notifications of trait changes.

    Static handlers can be created by creating methods on a HasTraits subclass with the naming convention ‘_[traitname]_changed’. Thus, to create static handler for the trait ‘a’, create the method _a_changed(self, name, old, new) (fewer arguments can be used, see below).

    Parameters :

    handler : callable

    > A callable that is called when a trait changes. Its signature can be handler(), handler(name), handler(name, new) or handler(name, old, new).

    name : list, str, None

    > If None, the handler will apply to all traits. If a list of str, handler will apply to all names in the list. If a str, the handler will apply just to that name.

    remove : bool

    > If False (the default), then install the handler. If True then unintall it.

  `option_description`

    A trait for unicode strings.

  `parse_command_line`(argv=None)

    Parse the command line arguments.

  `print_alias_help`()

    Print the alias part of the help.

  `print_description`()

    Print the application description.

  `print_examples`()

    Print usage and examples.

    This usage string goes at the end of the command line help string and should contain examples of the application’s usage.

  `print_flag_help`()

    Print the flag part of the help.

  `print_help`(classes=False)

    Print the help for each Configurable class in self.classes.

    If classes=False (the default), only flags and aliases are printed.

  `print_options`()
  `print_subcommands`()

    Print the subcommand part of the help.

  `print_version`()

    Print the version string.

  `start`()

    Start the app mainloop.

    Override in subclasses.

  `subapp`

    A trait whose value must be an instance of a specified class.

    The value can also be an instance of a subclass of the specified class.

  `subcommand_description`

    A trait for unicode strings.

  `subcommands`

    An instance of a Python dict.

  `trait_metadata`(traitname, key)

    Get metadata values for trait by key.

  `trait_names`(**metadata)

    Get a list of all the names of this classes traits.

  `traits`(**metadata)

    Get a list of all the traits of this class.

    The TraitTypes returned don’t know anything about the values that the various HasTrait’s instances are holding.

    This follows the same algorithm as traits does and does not allow for any simple way of specifying merely that a metadata name exists, but has any value. This is because get_metadata returns None if a metadata key doesn’t exist.

  `update_config`(config)

    Fire the traits events when the config is updated.

  `version`

    A trait for unicode strings.

### `ApplicationError`

class `IPython.config.application.``ApplicationError`

  Bases: `exceptions.Exception`

  `__init__`()

    x.__init__(...) initializes x; see x.__class__.__doc__ for signature

  `args`
  `message`

## Function

`IPython.config.application.``boolean_flag`(name, configurable, set_help='', unset_help='')

  Helper for building basic –trait, –no-trait flags.

  Parameters :

  name : str

  > The name of the flag.

  configurable : str

  > The ‘Class.trait’ string of the trait to be set/unset with the flag

  set_help : unicode

  > help string for –name flag

  unset_help : unicode

  > help string for –no-name flag

  Returns :

  cfg : dict

  > A dict with two keys: ‘name’, and ‘no-name’, for setting and unsetting the trait, respectively.

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