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# core.application

## Module: `core.application`

Inheritance diagram for `IPython.core.application`:

An application for IPython.

All top-level applications should use the classes in this module for handling configuration and creating componenets.

The job of an `Application` is to create the master configuration object and then create the configurable objects, passing the config to them.

Authors:

- Brian Granger
- Fernando Perez
- Min RK

## `BaseIPythonApplication`

class `IPython.core.application.``BaseIPythonApplication`(**kwargs)

  Bases: `IPython.config.application.Application`

  `__init__`(**kwargs)
  `aliases`

    An instance of a Python dict.

  `auto_create`

    A boolean (True, False) trait.

  `builtin_profile_dir`

    A trait for unicode strings.

  classmethod `class_config_section`()

    Get the config class config section

  classmethod `class_get_help`(inst=None)

    Get the help string for this class in ReST format.

    If inst is given, it’s current trait values will be used in place of class defaults.

  classmethod `class_get_trait_help`(trait, inst=None)

    Get the help string for a single trait.

    If inst is given, it’s current trait values will be used in place of the class default.

  classmethod `class_print_help`(inst=None)

    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.

  `config_file_name`

    A trait for unicode strings.

  `config_file_paths`

    An instance of a Python list.

  `config_file_specified`

    A boolean (True, False) trait.

  `config_files`

    An instance of a Python list.

  `copy_config_files`

    A boolean (True, False) trait.

  `crash_handler_class`

    A trait whose value must be a subclass of a specified class.

  `description`

    A trait for unicode strings.

  `examples`

    A trait for unicode strings.

  `excepthook`(etype, evalue, tb)

    this is sys.excepthook after init_crashhandler

    set self.verbose_crash=True to use our full crashhandler, instead of a regular traceback with a short message (crash_handler_lite)

  `exit`(exit_status=0)
  `extra_args`

    An instance of a Python list.

  `flags`

    An instance of a Python dict.

  `flatten_flags`()

    flatten flags and aliases, so cl-args override as expected.

    This prevents issues such as an alias pointing to InteractiveShell, but a config file setting the same trait in TerminalInteraciveShell getting inappropriate priority over the command-line arg.

    Only aliases with exactly one descendent in the class list will be promoted.

  `generate_config_file`()

    generate default config file from Configurables

  `init_config_files`()

    [optionally] copy default config files into profile dir.

  `init_crash_handler`()

    Create a crash handler, typically setting sys.excepthook to it.

  `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.

  `init_profile_dir`()

    initialize the profile dir

  `initialize`(argv=None)
  `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

  `ipython_dir`

    A trait for unicode strings.

  `keyvalue_description`

    A trait for unicode strings.

  `load_config_file`(suppress_errors=True)

    Load the config file.

    By default, errors in loading config are handled, and a warning printed on screen. For testing, the suppress_errors option is set to False, so errors will make tests fail.

  `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.

  `overwrite`

    A boolean (True, False) trait.

  `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.

  `profile`

    A trait for unicode strings.

  `stage_default_config_file`()

    auto generate default config file, and stage it into the profile.

  `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.

  `verbose_crash`

    A boolean (True, False) trait.

  `version`

    A trait for unicode strings.

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