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:
"""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.
Use pip:
python -m pip install docopt-ng
docopt-ng is tested with Python 3.7+.
def docopt(
docstring: str,
argv: list[str] | str | None = None,
default_help: bool = True,
version: Any = None,
options_first: bool = False,
) -> ParsedOptions:
docopt takes a docstring, and 4 optional arguments:
docstring is a string that contains a help message that will be
used to create the option parser.
The simple rules of how to write such a help message
are given in next sections. Typically you would just use __doc__.
argv is an optional argument vector; by default docopt 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 default True, specifies whether the parser should
automatically print the help message (supplied as doc) 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), set
help=False.
version, by default None, 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
docoptis set to automatically handle-h,--helpand--versionoptions, you still need to mention them in usage pattern for this to work. Also, for your users to know about them.
options_first, by default False. If set to True 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.
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 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 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:
my_program.py CONTENT-PATH or words
surrounded by angular brackets: my_program.py <content-path>.-), 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).--options or <arguments> or ARGUMENTS, plus two
special commands: dash "-" and double dash "--" (see below).Use the following constructs to specify patterns:
my_program.py [-hvqo FILE]my_program.py --path=<path> <file>... is the same as
my_program.py (--path=<path> <file>...). (Note, "required options"
might be not a good idea for your users).my_program.py (--clockwise | --counter-clockwise) TIME. Group them
using [ ] if none of the mutually-exclusive elements are
required: my_program.py [--left | --right]....), e.g. my_program.py FILE ... means one or more
FILE-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.[--]". 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 that
stdin 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 consist of a list of options that you put below your usage patterns.
It is necessary to list option descriptions in order to specify:
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]
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.
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 .
FAQs
Jazzband-maintained fork of docopt, the humane command line arguments parser.
We found that docopt-ng demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 2 open source maintainers collaborating on the project.
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