yamlargparse 1.13.0

Parsing of command line options, yaml config files and/or environment variables based on argparse.

yamlargparse python module

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This module is an extension to python’s argparse which simplifies parsing of configuration options from command line arguments, yaml configuration files, environment variables and hard-coded defaults.

The aim is similar to other projects such as configargparse, yconf and confuse. The obvious question is, why yet another module similar to many already existing ones? The answer is simply that none of the existing projects had the exact features we wanted and after analyzing the alternatives it seemed simpler to create a new module.

Features

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• Parsers are configured just like with python’s argparse, thus it has a gentile learning curve.

• Not exclusively intended for parsing command line arguments. The module has functions to parse environment variables and yaml config files.

• Support for nested namespaces which makes it possible to parse yaml with non-flat hierarchies.

• Parsing of relative paths within yaml files.

• Configuration settings are overridden based on the following precedence.

  • Parsing command line: command line arguments (might include config file) > environment variables > defaults.

  • Parsing yaml: config file values > environment variables > defaults.

  • Parsing environment: environment variables > defaults.

Using the module

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A parser is created just like it is done with argparse. You import the module, create a parser object and then add arguments to it. A simple example would be:

import yamlargparse parser = yamlargparse.ArgumentParser( prog = 'app', description = 'Description for my app.')

parser.add_argument('--opt1', type = int, default = 0, help = 'Help for option 1.')

parser.add_argument('--opt2', type = float, default = 1.0, help = 'Help for option 2.')

After creating the parser, you can use it to parse command line arguments with the "yamlargparse.ArgumentParser.parse_args()" function, after which you get an object with the parsed values or defaults available as attributes. For illustrative purposes giving to "parse_args()" a list of arguments (instead of automatically getting them from the command line arguments), with the parser from above you would observe:

cfg = parser.parse_args(['--opt2', '2.3']) cfg.opt1, type(cfg.opt1) (0, <class 'int'>) cfg.opt2, type(cfg.opt2) (2.3, <class 'float'>)

Nested namespaces

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A difference with respect to the basic argparse is that it by using dot notation in the argument names, you can define a hierarchy of nested namespaces. So for example you could do the following:

parser = yamlargparse.ArgumentParser(prog='app') parser.add_argument('--lev1.opt1', default='from default 1') parser.add_argument('--lev1.opt2', default='from default 2') cfg = parser.get_defaults() cfg.lev1.opt1 'from default 2' cfg.lev1.opt2 'from default 2'

Environment variables

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The yamlargparse parsers by default also get values from environment variables. In the case of environment variables, the parser checks existing variables whose name is of the form "[PROG_][LEV__]*OPT", that is all in upper case, first only if set the name of the program followed by underscore and then the argument name replacing dots with two underscores. Using the parser from the Nested namespaces section above, in your shell you would set the environment variables as:

export APP_LEV1__OPT1='from env 1' export APP_LEV1__OPT2='from env 2'

Then in python the parser would use these variables, unless overridden by the command line arguments, that is:

parser = yamlargparse.ArgumentParser(prog='app') parser.add_argument('--lev1.opt1', default='from default 1') parser.add_argument('--lev1.opt2', default='from default 2') cfg = parser.parse_args(['--lev1.opt1', 'from arg 1']) cfg.lev1.opt1 'from arg 1' cfg.lev1.opt2 'from env 2'

There is also the "yamlargparse.ArgumentParser.parse_env()" function to only parse environment variables, which might be useful for some use cases in which there is no command line call involved.

YAML configuration files

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An important feature of this module is the parsing of yaml files. The dot notation hierarchy of the arguments (see Nested namespaces) are used for the expected structure of the yaml files.

When parsing command line arguments, it is possible to add a yaml configuration file path argument. The yaml file would be read and parsed in the specific position among the command line arguments, so the arguments after would override the values from the yaml file. Again using the parser from the Nested namespaces section above, for example we could have the following yaml:

File: example.yaml

lev1: opt1: from yaml 1 opt2: from yaml 2

Then in python adding a yaml file argument and parsing some example arguments, the following would be observed:

parser = yamlargparse.ArgumentParser(prog='app') parser.add_argument('--lev1.opt1', default='from default 1') parser.add_argument('--lev1.opt2', default='from default 2') parser.add_argument('--cfg', action=yamlargparse.ActionConfigFile) cfg = parser.parse_args(['--lev1.opt1', 'from arg 1', '--cfg', 'example.yaml', '--lev1.opt2', 'from arg 2']) cfg.lev1.opt1 'from yaml 1' cfg.lev1.opt2 'from arg 2'

There are also functions "yamlargparse.ArgumentParser.parse_yaml_path()" and "yamlargparse.ArgumentParser.parse_yaml_string()" to only parse a yaml file or yaml contained in a string respectively.

Parsing paths

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For some use cases it is necessary to parse file paths, checking its existence and access permissions, but not necessarily opening the file. Moreover, a file path could be included in a yaml file as relative with respect to the yaml file’s location. After parsing it should be easy to access the parsed file path without having to consider the location of the yaml file. To help in these situations yamlargparse includes the "ActionPath" and the "ActionPathList" classes.

For example suppose you have a directory with a configuration file "app/config.yaml" and some data "app/data/info.db". The contents of the yaml file is the following:

File: config.yaml

databases: info: data/info.db

To create a parser that checks that the value of "databases.info" exists and is readable, the following could be done:

parser = yamlargparse.ArgumentParser(prog='app') parser.add_argument('--databases.info', action=yamlargparse.ActionPath(mode='r')) cfg = parser.parse_yaml('app/config.yaml')

After parsing it is possible to get both the original relative path as included in the yaml file, or the corresponding absolute path:

cfg.databases.info(absolute=False) 'data/info.db' cfg.databases.info() '/YOUR_CWD/app/data/info.db'

Likewise directories can also be parsed by including in the mode the "'d'" flag, e.g. "ActionPath(mode='drw')".

An argument with "ActionPath" can be given "nargs='+'" to parse multiple paths. But it might also be wanted to parse a list of paths found in a plain text file or from stdin. For this the "ActionPathList" is used and as argument either the path to a file listing the paths is given or the special "'-'" string for reading the list from stdin. For for example:

parser.add_argument('--list', action=yamlargparse.ActionPathList(mode='r')) cfg = parser.parse_args(['--list', 'paths.lst') # Text file with paths cfg = parser.parse_args(['--list', '-') # List from stdin

Parsing with another parser

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Sometimes an element in a yaml file could be a path to another yaml file with a complex structure which should also be parsed. To handle these cases there is the "ActionParser" which receives as argument a yamlargparse parser object. For example:

parser.add_argument('--complex.node', action=yamlargparse.ActionParser(parser=node_parser))

Comparison operators

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It is quite common that when parsing a number, its range should be limited. To ease these cases the module includes the "ActionOperators". Some examples of arguments that can be added using this action are the following:

Larger than zero

parser.add_argument('--op1', action=yamlargparse.ActionOperators(expr=('>', 0)))

Between 0 and 10

parser.add_argument('--op2', action=yamlargparse.ActionOperators(expr=[('>=', 0), ('<=', 10)]))

Either larger than zero or 'off' string

def int_or_off(x): return x if x == 'off' else int(x) parser.add_argument('--op3', action=yamlargparse.ActionOperators(expr=[('>', 0), ('==', 'off')], join='or', type=int_or_off))

API Reference

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class yamlargparse.ArgumentParser(prog=None, usage=None, description=None, epilog=None, parents=[], formatter_class=<class 'argparse.HelpFormatter'>, prefix_chars='-', fromfile_prefix_chars=None, argument_default=None, conflict_handler='error', add_help=True, allow_abbrev=True)

Bases: "argparse.ArgumentParser"

Extension to python’s argparse which simplifies parsing of configuration options from command line arguments, yaml configuration files, environment variables and hard-coded defaults.

parse_args(args=None, namespace=None, env: bool = True, nested: bool = True)

  Parses command line argument strings.

  All the arguments from argparse.ArgumentParser.parse_args are
  supported. Additionally it accepts:

  Parameters:
     * **env** (*bool*) – Whether to merge with the parsed
       environment.

     * **nested** (*bool*) – Whether the namespace should be
       nested.

  Returns:
     An object with all parsed values as nested attributes.

  Return type:
     SimpleNamespace

parse_yaml_path(yaml_path: str, env: bool = True, defaults: bool = True, nested: bool = True) -> types.SimpleNamespace

  Parses a yaml file given its path.

  Parameters:
     * **yaml_path** (*str*) – Path to the yaml file to parse.

     * **env** (*bool*) – Whether to merge with the parsed
       environment.

     * **defaults** (*bool*) – Whether to merge with the
       parser’s defaults.

     * **nested** (*bool*) – Whether the namespace should be
       nested.

  Returns:
     An object with all parsed values as nested attributes.

  Return type:
     SimpleNamespace

parse_yaml_string(yaml_str: str, env: bool = True, defaults: bool = True, nested: bool = True) -> types.SimpleNamespace

  Parses yaml given as a string.

  Parameters:
     * **yaml_str** (*str*) – The yaml content.

     * **env** (*bool*) – Whether to merge with the parsed
       environment.

     * **defaults** (*bool*) – Whether to merge with the
       parser’s defaults.

     * **nested** (*bool*) – Whether the namespace should be
       nested.

  Returns:
     An object with all parsed values as attributes.

  Return type:
     SimpleNamespace

dump_yaml(cfg: Union[types.SimpleNamespace, dict]) -> str

  Generates a yaml string for a configuration object.

  Parameters:
     **cfg** (*SimpleNamespace | dict*) – The configuration object
     to dump.

  Returns:
     The configuration in yaml format.

  Return type:
     str

parse_env(env: Dict[str, str] = None, defaults: bool = True, nested: bool = True) -> types.SimpleNamespace

  Parses environment variables.

  Parameters:
     * **env** (*Dict**[**str**, **str**]*) – The environment
       object to use, if None *os.environ* is used.

     * **defaults** (*bool*) – Whether to merge with the
       parser’s defaults.

     * **nested** (*bool*) – Whether the namespace should be
       nested.

  Returns:
     An object with all parsed values as attributes.

  Return type:
     SimpleNamespace

get_defaults(nested: bool = True) -> types.SimpleNamespace

  Returns a namespace with all default values.

  Parameters:
     **nested** (*bool*) – Whether the namespace should be nested.

  Returns:
     An object with all default values as attributes.

  Return type:
     SimpleNamespace

add_argument_group(*args, name: str = None, **kwargs)

  Adds a group to the parser.

  All the arguments from
  argparse.ArgumentParser.add_argument_group are supported.
  Additionally it accepts:

  Parameters:
     **name** (*str*) – Name of the group. If set the group object
     will be included in the parser.groups dict.

  Returns:
     The group object.

check_config(cfg: Union[types.SimpleNamespace, dict], skip_none: bool = False)

  Checks that the content of a given configuration object conforms
  with the parser.

  Parameters:
     * **cfg** (*SimpleNamespace | dict*) – The configuration
       object to check.

     * **skip_none** (*bool*) – Whether to skip checking of
       values that are None.

static merge_config(cfg_from: Union[types.SimpleNamespace, Dict[str, Any]], cfg_to: Union[types.SimpleNamespace, Dict[str, Any]]) -> Union[types.SimpleNamespace, Dict[str, Any]]

  Merges the first configuration into the second configuration.

  Parameters:
     * **cfg_from** (*SimpleNamespace | dict*) – The
       configuration from which to merge.

     * **cfg_to** (*SimpleNamespace | dict*) – The configuration
       into which to merge.

  Returns:
     The merged configuration with same type as cfg_from.

  Return type:
     SimpleNamespace | dict

class yamlargparse.ActionConfigFile(**kwargs)

Bases: "argparse.Action"

Action to indicate that an argument is a configuration file.

class yamlargparse.ActionYesNo(**kwargs)

Bases: "argparse.Action"

Paired action –opt, –no_opt to set True or False respectively.

class yamlargparse.ActionParser(**kwargs)

Bases: "argparse.Action"

Action to parse option with a given yamlargparse parser optionally loading from yaml file if string value.

Parameters: parser (ArgumentParser) – A yamlargparse parser to parse the option with.

class yamlargparse.ActionOperators(**kwargs)

Bases: "argparse.Action"

Action to restrict a number range with comparison operators.

Parameters: * expr (tuple* or *list of tuples) – Pairs of operators (> >= < <= == !=) and reference values, e.g. [(‘>=’, 1),…].

  * **join** (*str*) – How to combine multiple comparisons, must
    be ‘or’ or ‘and’ (default=’and’).

  * **type** (*type*) – The value type (default=int).

class yamlargparse.ActionPath(**kwargs)

Bases: "argparse.Action"

Action to check and store a file path.

Parameters: mode (str) – The required type and access permissions among [drwx] as a keyword argument, e.g. ActionPath(mode=’drw’).

class yamlargparse.ActionPathList(**kwargs)

Bases: "argparse.Action"

Action to check and store a list of file paths read from a plain text file or stream.

Note: The paths in the list if relative should be with respect to the current working directory, not with respect to the directory where the list is.

Parameters: * mode (str) – The required type and access permissions among [drwx] as a keyword argument, e.g. ActionPathList(mode=’r’).

  * **rel** (*str*) – Whether relative paths are with respect to
    current working directory ‘cwd’ or the list’s parent directory
    ‘list’ (default=’cwd’).

class yamlargparse.Path(path, mode: str = 'r', cwd: str = None)

Bases: "object"

Stores a (possibly relative) path and the corresponding absolute path.

When a Path instance is created it is checked that: the path exists, whether it is a file or directory and whether has the required access permissions (d=directory, r=readable, w=writeable, x=executable). The absolute path can be obtained without having to remember the working directory from when the object was created.

Parameters: * path (str) – The path to check and store.

  * **mode** (*str*) – The required type and access permissions
    among [drwx].

  * **cwd** (*str*) – Working directory for relative paths. If
    None, then os.getcwd() is used.

Args called: absolute (bool): If false returns the original path given, otherwise the corresponding absolute path.

License

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The MIT License (MIT)

Copyright (c) 2019-present, Mauricio Villegas [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.