Traitlets config API reference#

class traitlets.config.Configurable(**kwargs: Any)#

classmethod class_config_rst_doc() → str#

Generate rST documentation for this class’ config options.

Excludes traits defined on parent classes.

classmethod class_config_section(classes: Sequence[type[HasTraits]] | None = None) → str#

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: HasTraits | None = None) → str#

Get the help string for this class in ReST format.

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

classmethod class_get_trait_help(trait: TraitType[Any, Any], inst: HasTraits | None = None, helptext: str | None = None) → str#

Get the helptext string for a single trait.

Parameters:

inst – If given, its 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: HasTraits | None = None) → None#: Get the help string for a single trait and print it.

classmethod section_names() → list[str]#: return section names as a list

update_config(config: Config) → None#: Update config and load the new values

class traitlets.config.SingletonConfigurable(**kwargs: Any)#

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() → None#: unset _instance for this class and singleton parents.

classmethod initialized() → bool#: Has an instance been created?

classmethod instance(*args: Any, **kwargs: Any) → CT#

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 retrieved using the base class instance:

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

class traitlets.config.LoggingConfigurable(**kwargs: Any)#

A parent class for Configurables that log.

Subclasses have a log trait, and the default behavior is to get the logger from the currently running Application.

log#: Logger or LoggerAdapter instance

class traitlets.config.JSONFileConfigLoader(filename: str, path: str | None = None, **kw: Any)#

A JSON file loader for config

Can also act as a context manager that rewrite the configuration file to disk on exit.

Example:

with JSONFileConfigLoader('myapp.json','/home/jupyter/configurations/') as c:
    c.MyNewConfigurable.new_value = 'Updated'

load_config() → Config#: Load the config from a file and return it as a Config object.

class traitlets.config.Application(**kwargs: Any)#

A singleton application with full configuration support.

cli_config#

The subset of our configuration that came from the command-line

We re-load this configuration after loading config files, to ensure that it maintains highest priority.

document_config_options() → str#

Generate rST format documentation for the config options this application

Returns a multiline string.

emit_alias_help() → Generator[str, None, None]#: Yield the lines for alias part of the help.

emit_description() → Generator[str, None, None]#: Yield lines with the application description.

emit_examples() → Generator[str, None, None]#

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() → Generator[str, None, None]#: Yield the lines for the flag part of the help.

emit_help(classes: bool = False) → Generator[str, None, None]#

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: bool) → Generator[str, None, None]#

Yield the very bottom lines of the help message.

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

emit_options_help() → Generator[str, None, None]#: Yield the lines for the options part of the help.

emit_subcommands_help() → Generator[str, None, None]#: Yield the lines for the subcommand part of the help.

flatten_flags() → tuple[dict[str, Any], dict[str, Any]]#

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: List[Type[Configurable]] | None = None) → str#: generate default config file from Configurables

get_default_logging_config() → Dict[str, Any]#

Return the base logging configuration.

The default is to log to stderr using a StreamHandler, if no default handler already exists.

The log handler level starts at logging.WARN, but this can be adjusted by setting the log_level attribute.

The logging_config trait is merged into this allowing for finer control of logging.

initialize(argv: List[str] | None = None) → None#

Do the basic steps to configure me.

Override in subclasses.

initialize_subcommand(subc: str, argv: List[str] | None = None) → None#: Initialize a subcommand with argv.

json_config_loader_class#: alias of JSONFileConfigLoader

classmethod launch_instance(argv: List[str] | None = None, **kwargs: Any) → None#

Launch a global instance of this Application

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

load_config_environ() → None#: Load config files by environment.

load_config_file(filename: str, path: str | Sequence[str | None] | None = None) → None#: Load config files by filename and path.

property loaded_config_files: list[str]#: Currently loaded configuration files

log_datefmt#: The date format used by logging formatters for %(asctime)s

log_format#: The Logging format template

log_level#: Set the log level by value or name.

logging_config#

Configure additional log handlers.

The default stderr logs handler is configured by the log_level, log_datefmt and log_format settings.

This configuration can be used to configure additional handlers (e.g. to output the log to a file) or for finer control over the default handlers.

If provided this should be a logging configuration dictionary, for more information see: https://docs.python.org/3/library/logging.config.html#logging-config-dictschema

This dictionary is merged with the base logging configuration which defines the following:

A logging formatter intended for interactive use called console.
A logging handler that writes to stderr called console which uses the formatter console.
A logger with the name of this application set to DEBUG level.

This example adds a new handler that writes to a file:

c.Application.logging_config = {
    "handlers": {
        "file": {
            "class": "logging.FileHandler",
            "level": "DEBUG",
            "filename": "<path/to/file>",
        }
    },
    "loggers": {
        "<application-name>": {
            "level": "DEBUG",
            # NOTE: if you don't list the default "console"
            # handler here then it will be disabled
            "handlers": ["console", "file"],
        },
    },
}

parse_command_line(argv: List[str] | None = None) → None#: Parse the command line arguments.

print_alias_help() → None#: Print the alias parts of the help.

print_description() → None#: Print the application description.

print_examples() → None#: Print usage and examples (see emit_examples()).

print_flag_help() → None#: Print the flag part of the help.

print_help(classes: bool = False) → None#

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

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

print_options() → None#: Print the options part of the help.

print_subcommands() → None#: Print the subcommand part of the help.

print_version() → None#: Print the version string.

python_config_loader_class#: alias of PyFileConfigLoader

show_config#: Instead of starting the Application, dump configuration to stdout

show_config_json#: Instead of starting the Application, dump configuration to stdout (as JSON)

start() → None#

Start the app mainloop.

Override in subclasses.

start_show_config() → None#: start function used when show_config is True

class traitlets.config.Config(*args: Any, **kwds: Any)#

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: Config) → dict[str, Any]#

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: Any) → bool#: True if the dictionary has the specified key, else False.

merge(other: Any) → None#: merge another config object into this one

class traitlets.config.loader.LazyConfigValue(**kwargs: Any)#

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: Any) → None#: Add an item to a set

append(obj: Any) → None#: Append an item to a List

extend(other: Any) → None#: Extend a list

get_value(initial: Any) → Any#

construct the value from the initial one

after applying any insert / extend / update changes

merge_into(other: Any) → Any#

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: Any) → None#: like list.extend, but for the front

to_dict() → dict[str, Any]#

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: Any) → None#: Update either a set or dict

class traitlets.config.loader.KVArgParseConfigLoader(argv: list[str] | None = None, aliases: dict[str, str] | None = None, flags: dict[str, str] | None = None, log: Any = None, classes: list[type[Any]] | None = None, subcommands: Dict[str, Any] | None = None, *parser_args: Any, **parser_kw: Any)#

A config loader that loads aliases and flags with argparse,

as well as arbitrary –Class.trait value

__init__(argv: list[str] | None = None, aliases: dict[str, str] | None = None, flags: dict[str, str] | None = None, log: Any = None, classes: list[type[Any]] | None = None, subcommands: Dict[str, Any] | None = None, *parser_args: Any, **parser_kw: Any) → None#

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 traitlets names for CLI parsing
flags (dict of str to str) – Dict of flags to full traitlets names for CLI parsing
log – Passed to ConfigLoader

Returns:

config – The resulting Config object.

Return type:

Config

load_config(argv: list[str] | None = None, aliases: ~typing.Any = None, flags: ~typing.Any = <Sentinel deprecated>, classes: ~typing.Any = None) → Config#

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, instantiate the config loader with the flags.