Traitlets config API reference

class traitlets.config.Configurable(**kwargs)

classmethod class_config_rst_doc()

Generate rST documentation for this class’ config options.

Excludes traits defined on parent classes.

classmethod class_config_section(classes=None)

Get the config section for this class.

Parameters

classes (list, optional) – The list of other classes in the config file. Used to reduce redundant information.

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, helptext=None)

Get the helptext string for a single trait.

Parameters

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

• helptext – If not given, uses the help attribute of the current trait.

classmethod class_print_help(inst=None)

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

classmethod section_names()

return section names as a list

update_config(config)

Update config and load the new values

class traitlets.config.SingletonConfigurable(**kwargs)

A configurable that only allows one instance.

This class is for classes that should only have one instance of itself or any subclass. To create and retrieve such a class use the SingletonConfigurable.instance() method.

classmethod clear_instance()

unset _instance for this class and singleton parents.

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 traitlets.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

class traitlets.config.Application(**kwargs)

A singleton application with full configuration support.

aliases = {'log-level': 'Application.log_level'}

the alias map for configurables Keys might strings or tuples for additional options; single-letter alias accessed like -v. Values might be like “Class.trait” strings of two-tuples: (Class.trait, help-text).

document_config_options()

Generate rST format documentation for the config options this application

Returns a multiline string.

emit_alias_help()

Yield the lines for alias part of the help.

emit_description()

Yield lines with the application description.

emit_examples()

Yield lines with the 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.

emit_flag_help()

Yield the lines for the flag part of the help.

emit_help(classes=False)

Yield the help-lines for each Configurable class in self.classes.

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

emit_help_epilogue(classes)

Yield the very bottom lines of the help message.

If classes=False (the default), print –help-all msg.

emit_options_help()

Yield the lines for the options part of the help.

emit_subcommands_help()

Yield the lines for the subcommand part of the help.

flatten_flags()

Flatten flags and aliases for loaders, 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. Also, loaders expect (key: longname) and not ``key: (longname, help) items.

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

generate_config_file(classes=None)

generate default config file from Configurables

initialize(argv=None)

Do the basic steps to configure me.

Override in subclasses.

initialize_subcommand(subc, argv=None)

Initialize a subcommand with argv.

json_config_loader_class

alias of traitlets.config.loader.JSONFileConfigLoader

classmethod launch_instance(argv=None, **kwargs)

Launch a global instance of this Application

If a global instance already exists, this reinitializes and starts it

load_config_file(filename, path=None)

Load config files by filename and path.

property loaded_config_files

Currently loaded configuration files

parse_command_line(argv=None)

Parse the command line arguments.

print_alias_help()

Print the alias parts of the help.

print_description()

Print the application description.

print_examples()

Print usage and examples (see emit_examples()).

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 the options part of the help.

print_subcommands()

Print the subcommand part of the help.

print_version()

Print the version string.

python_config_loader_class

alias of traitlets.config.loader.PyFileConfigLoader

start()

Start the app mainloop.

Override in subclasses.

start_show_config()

start function used when show_config is True

class traitlets.config.Config(*args, **kwds)

An attribute-based dict that can do smart merges.

Accessing a field on a config object for the first time populates the key with either a nested Config object for keys starting with capitals or LazyConfigValue for lowercase keys, allowing quick assignments such as:

c = Config()
c.Class.int_trait = 5
c.Class.list_trait.append("x")

collisions(other)

Check for collisions between two config objects.

Returns a dict of the form {“Class”: {“trait”: “collision message”}}`, indicating which values have been ignored.

An empty dict indicates no collisions.

copy() → a shallow copy of D

has_key(key)

True if the dictionary has the specified key, else False.

merge(other)

merge another config object into this one

class traitlets.config.loader.LazyConfigValue(**kwargs)

Proxy object for exposing methods on configurable containers

These methods allow appending/extending/updating to add to non-empty defaults instead of clobbering them.

Exposes:

• append, extend, insert on lists

• update on dicts

• update, add on sets

add(obj)

Add an item to a set

append(obj)

Append an item to a List

extend(other)

Extend a list

get_value(initial)

construct the value from the initial one

after applying any insert / extend / update changes

merge_into(other)

Merge with another earlier LazyConfigValue or an earlier container. This is useful when having global system-wide configuration files.

Self is expected to have higher precedence.

Parameters

other (LazyConfigValue or container) –

Returns

if other is also lazy, a reified container otherwise.

Return type

LazyConfigValue

prepend(other)

like list.extend, but for the front

to_dict()

return JSONable dict form of my data

Currently update as dict or set, extend, prepend as lists, and inserts as list of tuples.

update(other)

Update either a set or dict

class traitlets.config.loader.KVArgParseConfigLoader(argv=None, aliases=None, flags=None, log=None, classes=(), *parser_args, **parser_kw)

A config loader that loads aliases and flags with argparse,

as well as arbitrary –Class.trait value

__init__(argv=None, aliases=None, flags=None, log=None, classes=(), *parser_args, **parser_kw)

Create a config loader for use with argparse.

Parameters

• classes (optional, list) – The classes to scan for container config-traits and decide for their “multiplicity” when adding them as argparse arguments.

• argv (optional, list) – If given, used to read command-line arguments from, otherwise sys.argv[1:] is used.

• *parser_args (tuple) – A tuple of positional arguments that will be passed to the constructor of argparse.ArgumentParser.

• **parser_kw (dict) – A tuple of keyword arguments that will be passed to the constructor of argparse.ArgumentParser.

• aliases (dict of str to str) – Dict of aliases to full traitlests names for CLI parsing

• flags (dict of str to str) – Dict of flags to full traitlests names for CLI parsing

• log – Passed to ConfigLoader

Returns

config – The resulting Config object.

Return type

Config

load_config(argv=None, aliases=None, flags=<Sentinel deprecated>, classes=None)

Parse command line arguments and return as a Config object.

Parameters

• argv (optional, list) – If given, a list with the structure of sys.argv[1:] to parse arguments from. If not given, the instance’s self.argv attribute (given at construction time) is used.

• flags – Deprecated in traitlets 5.0, instanciate the config loader with the flags.