Awesome
docopt-ng creates magic command-line interfaces
docopt-ng is a fork of the original docopt, now maintained by the jazzband project. Now with maintenance, typehints, and complete test coverage!
docopt-ng helps you create beautiful command-line interfaces magically:
"""Naval Fate.
Usage:
naval_fate.py ship new <name>...
naval_fate.py ship <name> move <x> <y> [--speed=<kn>]
naval_fate.py ship shoot <x> <y>
naval_fate.py mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate.py (-h | --help)
naval_fate.py --version
Options:
-h --help Show this screen.
--version Show version.
--speed=<kn> Speed in knots [default: 10].
--moored Moored (anchored) mine.
--drifting Drifting mine.
"""
from docopt import docopt
if __name__ == "__main__":
argv = ["ship", "Guardian", "move", "100", "150", "--speed=15"]
arguments = docopt(__doc__, argv)
print(arguments)
results in:
{'--drifting': False,
'--help': False,
'--moored': False,
'--speed': '15',
'--version': False,
'<name>': ['Guardian'],
'<x>': '100',
'<y>': '150',
'mine': False,
'move': True,
'new': False,
'remove': False,
'set': False,
'ship': True,
'shoot': False}
Beat that! The option parser is generated based on the docstring above
that is passed to docopt
function. docopt
parses the usage pattern
("Usage: ..."
) and option descriptions (lines starting with dash
"-
") and ensures that the program invocation matches the usage
pattern; it parses options, arguments and commands based on that. The
basic idea is that a good help message has all necessary information in
it to make a parser.
Also, PEP 257 recommends putting help message in the module docstrings.
Installation
Use pip:
python -m pip install docopt-ng
docopt-ng is tested with Python 3.7+.
API
def docopt(
docstring: str | None = None,
argv: list[str] | str | None = None,
default_help: bool = True,
version: Any = None,
options_first: bool = False,
more_magic: bool = False,
) -> ParsedOptions:
docopt
takes 6 optional arguments:
-
docstring
could be a module docstring (__doc__
) or some other string that contains a help message that will be parsed to create the option parser. The simple rules of how to write such a help message are given in next sections. If it is None (not provided), the calling scope will be interrogated for a docstring. -
argv
is an optional argument vector; by defaultdocopt
uses the argument vector passed to your program (sys.argv[1:]
). Alternatively you can supply a list of strings like["--verbose", "-o", "hai.txt"]
, or a single string that will be split on spaces like"--verbose -o hai.txt"
. -
default_help
, by defaultTrue
, specifies whether the parser should automatically print the help message (supplied asdoc
) and terminate, in case-h
or--help
option is encountered (options should exist in usage pattern, more on that below). If you want to handle-h
or--help
options manually (as other options), sethelp=False
. -
version
, by defaultNone
, is an optional argument that specifies the version of your program. If supplied, then, (assuming--version
option is mentioned in usage pattern) when parser encounters the--version
option, it will print the supplied version and terminate.version
could be any printable object, but most likely a string, e.g."2.1.0rc1"
.Note, when
docopt
is set to automatically handle-h
,--help
and--version
options, you still need to mention them in usage pattern for this to work. Also, for your users to know about them. -
options_first
, by defaultFalse
. If set toTrue
will disallow mixing options and positional argument. I.e. after first positional argument, all arguments will be interpreted as positional even if the look like options. This can be used for strict compatibility with POSIX, or if you want to dispatch your arguments to other programs. -
more_magic
, by defaultFalse
. If set toTrue
more advanced efforts will be made to correct--long_form
arguments, ie:--hlep
will be corrected to--help
. Additionally, if not already defined, the variablearguments
will be created and populated in the calling scope.more_magic
is also set True ifdocopt()
is is aliased to a name containingmagic
ie) by built-infrom docopt import magic
or user-definedfrom docopt import docopt as magic_docopt_wrapper
for convenience.
The return value is a simple dictionary with options, arguments and
commands as keys, spelled exactly like in your help message. Long
versions of options are given priority. Furthermore, dot notation is
supported, with preceeding dashes (-
) and surrounding brackets (<>
)
ignored, for example arguments.drifting
or arguments.x
.
Help message format
Help message consists of 2 parts:
-
Usage pattern, e.g.:
Usage: my_program.py [-hso FILE] [--quiet | --verbose] [INPUT ...]
-
Option descriptions, e.g.:
-h --help show this -s --sorted sorted output -o FILE specify output file [default: ./test.txt] --quiet print less text --verbose print more text
Their format is described below; other text is ignored.
Usage pattern format
Usage pattern is a substring of doc
that starts with usage:
(case insensitive) and ends with a visibly empty line. Minimum
example:
"""Usage: my_program.py
"""
The first word after usage:
is interpreted as your program's name. You
can specify your program's name several times to signify several
exclusive patterns:
"""Usage: my_program.py FILE
my_program.py COUNT FILE
"""
Each pattern can consist of the following elements:
- <arguments>, ARGUMENTS. Arguments are specified as
either upper-case words, e.g.
my_program.py CONTENT-PATH
or words surrounded by angular brackets:my_program.py <content-path>
. - --options. Options are words started with dash (
-
), e.g.--output
,-o
. You can "stack" several of one-letter options, e.g.-oiv
which will be the same as-o -i -v
. The options can have arguments, e.g.--input=FILE
or-i FILE
or even-iFILE
. However it is important that you specify option descriptions if you want your option to have an argument, a default value, or specify synonymous short/long versions of the option (see next section on option descriptions). - commands are words that do not follow the described above
conventions of
--options
or<arguments>
orARGUMENTS
, plus two special commands: dash "-
" and double dash "--
" (see below).
Use the following constructs to specify patterns:
- [ ] (brackets) optional elements. e.g.:
my_program.py [-hvqo FILE]
- ( ) (parens) required elements. All elements that are not
put in [ ] are also required, e.g.:
my_program.py --path=<path> <file>...
is the same asmy_program.py (--path=<path> <file>...)
. (Note, "required options" might be not a good idea for your users). - | (pipe) mutually exclusive elements. Group them using (
) if one of the mutually exclusive elements is required:
my_program.py (--clockwise | --counter-clockwise) TIME
. Group them using [ ] if none of the mutually-exclusive elements are required:my_program.py [--left | --right]
. - ... (ellipsis) one or more elements. To specify that
arbitrary number of repeating elements could be accepted, use
ellipsis (
...
), e.g.my_program.py FILE ...
means one or moreFILE
-s are accepted. If you want to accept zero or more elements, use brackets, e.g.:my_program.py [FILE ...]
. Ellipsis works as a unary operator on the expression to the left. - [options] (case sensitive) shortcut for any options. You can use it if you want to specify that the usage pattern could be provided with any options defined below in the option-descriptions and do not want to enumerate them all in usage-pattern.
- "
[--]
". Double dash "--
" is used by convention to separate positional arguments that can be mistaken for options. In order to support this convention add "[--]
" to your usage patterns. - "
[-]
". Single dash "-
" is used by convention to signify thatstdin
is used instead of a file. To support this add "[-]
" to your usage patterns. "-
" acts as a normal command.
If your pattern allows to match argument-less option (a flag) several times:
Usage: my_program.py [-v | -vv | -vvv]
then number of occurrences of the option will be counted. I.e.
args["-v"]
will be 2
if program was invoked as my_program -vv
.
Same works for commands.
If your usage patterns allows to match same-named option with argument or positional argument several times, the matched arguments will be collected into a list:
Usage: my_program.py <file> <file> --path=<path>...
I.e. invoked with
my_program.py file1 file2 --path=./here --path=./there
the returned
dict will contain args["<file>"] == ["file1", "file2"]
and
args["--path"] == ["./here", "./there"]
.
Option descriptions format
Option descriptions consist of a list of options that you put below your usage patterns.
It is necessary to list option descriptions in order to specify:
- synonymous short and long options,
- if an option has an argument,
- if option's argument has a default value.
The rules are as follows:
-
Every line in
doc
that starts with-
or--
(not counting spaces) is treated as an option description, e.g.:Options: --verbose # GOOD -o FILE # GOOD Other: --bad # BAD, line does not start with dash "-"
-
To specify that option has an argument, put a word describing that argument after space (or equals "
=
" sign) as shown below. Follow either <angular-brackets> or UPPER-CASE convention for options' arguments. You can use comma if you want to separate options. In the example below, both lines are valid, however you are recommended to stick to a single style.:-o FILE --output=FILE # without comma, with "=" sign -i <file>, --input <file> # with comma, without "=" sign
-
Use two spaces to separate options with their informal description:
--verbose More text. # BAD, will be treated as if verbose option had # an argument "More", so use 2 spaces instead -q Quit. # GOOD -o FILE Output file. # GOOD --stdout Use stdout. # GOOD, 2 spaces
-
If you want to set a default value for an option with an argument, put it into the option-description, in form
[default: <my-default-value>]
:--coefficient=K The K coefficient [default: 2.95] --output=FILE Output file [default: test.txt] --directory=DIR Some directory [default: ./]
-
If the option is not repeatable, the value inside
[default: ...]
will be interpreted as string. If it is repeatable, it will be splited into a list on whitespace:Usage: my_program.py [--repeatable=<arg> --repeatable=<arg>] [--another-repeatable=<arg>]... [--not-repeatable=<arg>] # will be ["./here", "./there"] --repeatable=<arg> [default: ./here ./there] # will be ["./here"] --another-repeatable=<arg> [default: ./here] # will be "./here ./there", because it is not repeatable --not-repeatable=<arg> [default: ./here ./there]
Examples
We have an extensive list of examples which cover every aspect of functionality of docopt-ng. Try them out, read the source if in doubt.
Development
We would love to hear what you think about docopt-ng on our issues page. Make pull requests, report bugs, and suggest ideas.
To setup your dev environment, fork this repo and clone it locally. We use pdm to manage the project, so install that first.
Then install dev requirements and the package itself as editable, then install the pre-commit hooks:
pdm sync -d -G dev
pdm run pre-commit install
Useful testing, linting, and formatting commands:
pdm run pytest
pdm run black .
pdm run ruff .