argdeco-JoshGoA 1.1.0

Unopinionated argparse wrapper

argdeco

Unopinionated argparse wrapper

NOTE: The EXACT same decorating order as regular argparse MUST be respected

Why argdeco?

There are so many libraries out there for writing command line utilities; why does argdeco exist?

This question is easy to answer: because there is not a single command line utility for Python out there which ticks the following boxes: (sound familiar?)

• supports class callback method decoration and method instance binding with class instance forwarding (thank you Graham Dumpleton for wrapt!)

• supports callback callable instance binding with context or parser instance forwarding

• shares the EXACT same API as argparse using decorators

API reference

• argdeco.argument_parser(wrapped=None, parser_class=argparse.ArgumentParser, ctx=False, prog=None, usage=None, description=None, epilog=None, parents=[], formatter_class=argparse.HelpFormatter, prefix_chars="-", fromfile_prefix_chars=None, argument_default=None, conflict_handler="error", add_help=True, allow_abbrev=True)

  • Create a new ArgumentParser object. All parameters should be passed as keyword arguments. Each parameter has its own more detailed description below, but in short they are:

    • wrapped - The callback callable (default: None)

    • parser_class - The class to instantiate the parser (default: argparse.ArgumentParser)

    • ctx - Pass the context or parser instance to the callback callable (default: False)

    • prog - The name of the program (default: sys.argv[0])

    • usage - The string describing the program usage (default: generated from arguments added to parser)

    • description - Text to display before the argument help (default: doc)

    • epilog - Text to display after the argument help (default: none)

    • parents - A list of ArgumentParser objects whose arguments should also be included

    • formatter_class - A class for customizing the help output

    • prefix_chars - The set of characters that prefix optional arguments (default: "-")

    • fromfile_prefix_chars - The set of characters that prefix files from which additional arguments should be read (default: None)

    • argument_default - The global default value for arguments (default: None)

    • conflict_handler - The strategy for resolving conflicting optionals (usually unnecessary)

    • add_help - Add a -h/--help option to the parser (default: True)

    • allow_abbrev - Allows long options to be abbreviated if the abbreviation is unambiguous. (default: True)

>>> import argdeco
>>> @argdeco.add_argument("--foo", help="foo help")
... @argdeco.argument_parser
... def parser(foo):
...     pass
...

>>> parser(["--help"])
usage: myprogram.py [-h] [--foo FOO]

optional arguments:
 -h, --help  show this help message and exit
 --foo FOO   foo help

• argdeco.add_argument(name or flags..., group=None, [, action][, nargs][, const][, default][, type][, choices][, required][, help][, metavar][, dest])

  • Define how a single command-line argument should be parsed. Each parameter has its own more detailed description below, but in short they are:

    • name or flags - Either a name or a list of option strings, e.g. foo or -f, --foo.

    • group - The group to add the argument. (default: None)

    • action - The basic type of action to be taken when this argument is encountered at the command line.

    • nargs - The number of command-line arguments that should be consumed.

    • const - A constant value required by some action and nargs selections.

    • default - The value produced if the argument is absent from the command line.

    • type - The type to which the command-line argument should be converted.

    • choices - A container of the allowable values for the argument.

    • required - Whether or not the command-line option may be omitted (optionals only).

    • help - A brief description of what the argument does.

    • metavar - A name for the argument in usage messages.

    • dest - The name of the attribute to be added to the object returned by parse_args().

• argdeco.add_subparsers(wrapped=None, [title][, description][, prog][, parser_class][, action][, option_string][, dest][, required][, help][, metavar])

  • Many programs split up their functionality into a number of sub-commands, for example, the svn program can invoke sub-commands like svn checkout, svn update, and svn commit. Splitting up functionality this way can be a particularly good idea when a program performs several different functions which require different kinds of command-line arguments. ArgumentParser supports the creation of such sub-commands with the add_subparsers() method. The add_subparsers() method is normally called with no arguments and returns a special action object. This object has a single method, add_parser(), which takes a command name and any ArgumentParser constructor arguments, and returns an ArgumentParser object that can be modified as usual.

  • Description of parameters:

    • wrapped - The callback callable (default: None)

    • title - title for the sub-parser group in help output; by default “subcommands” if description is provided, otherwise uses title for positional arguments

    • description - description for the sub-parser group in help output, by default None

    • prog - usage information that will be displayed with sub-command help, by default the name of the program and any positional arguments before the subparser argument

    • parser_class - class which will be used to create sub-parser instances, by default the class of the current parser (e.g. ArgumentParser)

    • action - the basic type of action to be taken when this argument is encountered at the command line

    • dest - name of the attribute under which sub-command name will be stored; by default None and no value is stored

    • required - Whether or not a subcommand must be provided, by default False (added in 3.7)

    • help - help for sub-parser group in help output, by default None

    • metavar - string presenting available sub-commands in help; by default it is None and presents sub-commands in form {cmd1, cmd2, ..}

>>> # create the top-level parser
...
>>> @argdeco.add_subparsers(help="sub-command help")
... @argdeco.add_argument("--foo", action="store_true", help="foo help")
... @argdeco.argument_parser(prog="PROG")
... def parser(**kwargs):
...     print(parser)
...     print(kwargs)
...

>>> # create the parser for the "a" command
...
>>> @argdeco.add_argument("bar", type=int, help="bar help")
... @argdeco.add_parser(parser, "a", help="a help")
... def parser_a(**kwargs):
...     print(parser_a)
...     print(kwargs)
...

>>> # create the parser for the "a" command
...
>>> @argdeco.add_argument("--baz", choices="XYZ", help="baz help")
... @argdeco.add_parser(parser, "b", help="b help")
... def parser_b(**kwargs):
...     print(parser_b)
...     print(kwargs)
...

>>> # parse some argument lists
...
>>> parser(["a", "12"])
ArgumentParser(prog="PROG a", usage=None, description=None, formatter_class=<class "argparse.HelpFormatter">, conflict_handler="error", add_help=True)
{"foo": False, "bar": 12}
>>> parser(["--foo", "b", "--baz", "Z"])
ArgumentParser(prog="PROG b", usage=None, description=None, formatter_class=<class "argparse.HelpFormatter">, conflict_handler="error", add_help=True)
{"foo": True, "baz": "Z"}

• argdeco.add_argument_group(title=None, description=None)

  • By default, ArgumentParser groups command-line arguments into “positional arguments” and “optional arguments” when displaying help messages. When there is a better conceptual grouping of arguments than this default one, appropriate groups can be created using the add_argument_group() method:

>>> @argdeco.add_argument("bar", group="group", help="bar help")
... @argdeco.add_argument("--foo", group="group", help="foo help")
... @argdeco.add_argument_group("group")
... @argdeco.argument_parser(prog="PROG", add_help=False)
... def parser(**kwargs):
...     pass
...
>>> parser.print_help()
usage: PROG [--foo FOO] bar

group:
  bar    bar help
  --foo FOO  foo help

• ardeco.add_mutually_exclusive_group(required=False)

>>> @argdeco.add_argument("--bar", group="group", action="store_false")
... @argdeco.add_argument("--foo", group="group", action="store_true")
... @argdeco.add_mutually_exclusive_group("group")
... @argdeco.argument_parser(prog="PROG")
... def parser(**kwargs):
...     print(kwargs)
...
>>> parser(["--foo"])
{"foo": True, "bar": True}
>>> parser(["--bar"])
{"foo": False, "bar": False}
>>> parser(["--foo", "--bar"])
usage: PROG [-h] [--foo | --bar]
PROG: error: argument --bar: not allowed with argument --foo

Advanced usage

Class method decoration

argdeco supports class callback method decoration, unlike the big majority of CLI decorator libraries, without any difference as regular callback callable decoration.

>>> class Prog:
...
...     @argdeco.argument_parser
...     def parser(self):
...         pass
...

Decorating a class will forward the arguments to the __init__ method (usually not the desired behaviour), as decorated callbacks will ALWAYS be treated as callables.

>>> @argdeco.argument_parser
... class Prog:
...     pass
...

Decorating the __call__ method will forward the arguments to the class itself, following standard decorator usage as specified by wrapt.

>>> class Prog:
...
...     @argdeco.argument_parser
...     def __call__(self):
...         pass
...

Context

Decorated callback callables can get access to the argparse context or parser instance.

>>> @argdeco.argument_parser(ctx=True, prog="PROG")
... def parser(ctx):
...     ctx.print_help()
...
>>> parser([])
usage: PROG [-h]

optional arguments:
  -h, --help  show this help message and exit

Class callback method context or parser instance forwarding is still respected on decorated class methods.

>>> class Prog:
...
...     @argdeco.argument_parser(ctx=True, prog="PROG")
...     def __call__(self, ctx):
...         ctx.print_help()
...
>>> prog = Prog()
>>> prog([])
usage: PROG [-h]

optional arguments:
  -h, --help  show this help message and exit