getopt — C-style parser for command line options

Código fuente: Lib/getopt.py

Nota

This module is considered feature complete. A more declarative and extensible alternative to this API is provided in the optparse module. Further functional enhancements for command line parameter processing are provided either as third party modules on PyPI, or else as features in the argparse module.

---

This module helps scripts to parse the command line arguments in sys.argv. It supports the same conventions as the Unix getopt() function (including the special meanings of arguments of the form “-” and “--“). Long options similar to those supported by GNU software may be used as well via an optional third argument.

Users who are unfamiliar with the Unix getopt() function should consider using the argparse module instead. Users who are familiar with the Unix getopt() function, but would like to get equivalent behavior while writing less code and getting better help and error messages should consider using the optparse module. See Choosing an argument parsing library for additional details.

Este módulo proporciona dos funciones y una excepción:

getopt.getopt(args, shortopts, longopts=[])

Parses command line options and parameter list. args is the argument list to be parsed, without the leading reference to the running program. Typically, this means sys.argv[1:]. shortopts is the string of option letters that the script wants to recognize, with options that require an argument followed by a colon (':') and options that accept an optional argument followed by two colons ('::'); i.e., the same format that Unix getopt() uses.

Nota

Unlike GNU getopt(), after a non-option argument, all further arguments are considered also non-options. This is similar to the way non-GNU Unix systems work.

longopts, if specified, must be a list of strings with the names of the long options which should be supported. The leading '--' characters should not be included in the option name. Long options which require an argument should be followed by an equal sign ('='). Long options which accept an optional argument should be followed by an equal sign and question mark ('=?'). To accept only long options, shortopts should be an empty string. Long options on the command line can be recognized so long as they provide a prefix of the option name that matches exactly one of the accepted options. For example, if longopts is ['foo', 'frob'], the option --fo will match as --foo, but --f will not match uniquely, so GetoptError will be raised.

El valor de retorno consta de dos elementos: el primero es una lista de pares (option, value); el segundo es la lista de argumentos del programa que quedan después de que se eliminó la lista de opciones (esta es una porción final de args). Cada par de opción y valor retornado tiene la opción como su primer elemento, con un guión para las opciones cortas (por ejemplo, '-x') o dos guiones para las opciones largas (por ejemplo, '--long-option'), y el argumento de la opción como su segundo elemento, o una cadena vacía si la opción no tiene argumento. Las opciones aparecen en la lista en el mismo orden en que se encontraron, lo que permite múltiples ocurrencias. Las opciones largas y cortas pueden ser mixtas.

Distinto en la versión 3.14: Optional arguments are supported.

getopt.gnu_getopt(args, shortopts, longopts=[])

Esta función funciona como getopt(), excepto que el modo de escaneo estilo GNU se usa por defecto. Esto significa que los argumentos opcionales y no opcionales pueden estar mezclados. La función getopt() detiene el procesamiento de opciones tan pronto como se encuentra un argumento no-opcionales.

If the first character of the option string is '+', or if the environment variable POSIXLY_CORRECT is set, then option processing stops as soon as a non-option argument is encountered.

If the first character of the option string is '-', non-option arguments that are followed by options are added to the list of option-and-value pairs as a pair that has None as its first element and the list of non-option arguments as its second element. The second element of the gnu_getopt() result is a list of program arguments after the last option.

Distinto en la versión 3.14: Support for returning intermixed options and non-option arguments in order.

exception getopt.GetoptError

This is raised when an unrecognized option is found in the argument list or when an option requiring an argument is given none. The argument to the exception is a string indicating the cause of the error. For long options, an argument given to an option which does not require one will also cause this exception to be raised. The attributes msg and opt give the error message and related option; if there is no specific option to which the exception relates, opt is an empty string.

exception getopt.error

Alias para GetoptError; para compatibilidad con versiones anteriores.

Un ejemplo que usa solo opciones de estilo Unix:

>>> import getopt
>>> args = '-a -b -cfoo -d bar a1 a2'.split()
>>> args
['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'abc:d:')
>>> optlist
[('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')]
>>> args
['a1', 'a2']

Usar nombres largos de opciones es igualmente fácil:

>>> s = '--condition=foo --testing --output-file abc.def -x a1 a2'
>>> args = s.split()
>>> args
['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'x', [
...     'condition=', 'output-file=', 'testing'])
>>> optlist
[('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x', '')]
>>> args
['a1', 'a2']

Optional arguments should be specified explicitly:

>>> s = '-Con -C --color=off --color a1 a2'
>>> args = s.split()
>>> args
['-Con', '-C', '--color=off', '--color', 'a1', 'a2']
>>> optlist, args = getopt.getopt(args, 'C::', ['color=?'])
>>> optlist
[('-C', 'on'), ('-C', ''), ('--color', 'off'), ('--color', '')]
>>> args
['a1', 'a2']

The order of options and non-option arguments can be preserved:

>>> s = 'a1 -x a2 a3 a4 --long a5 a6'
>>> args = s.split()
>>> args
['a1', '-x', 'a2', 'a3', 'a4', '--long', 'a5', 'a6']
>>> optlist, args = getopt.gnu_getopt(args, '-x:', ['long='])
>>> optlist
[(None, ['a1']), ('-x', 'a2'), (None, ['a3', 'a4']), ('--long', 'a5')]
>>> args
['a6']

In a script, typical usage is something like this:

import getopt, sys

def main():
    try:
        opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
    except getopt.GetoptError as err:
        # print help information and exit:
        print(err)  # will print something like "option -a not recognized"
        usage()
        sys.exit(2)
    output = None
    verbose = False
    for o, a in opts:
        if o == "-v":
            verbose = True
        elif o in ("-h", "--help"):
            usage()
            sys.exit()
        elif o in ("-o", "--output"):
            output = a
        else:
            assert False, "unhandled option"
    process(args, output=output, verbose=verbose)

if __name__ == "__main__":
    main()

Note that an equivalent command line interface could be produced with less code and more informative help and error messages by using the optparse module:

import optparse

if __name__ == '__main__':
    parser = optparse.OptionParser()
    parser.add_option('-o', '--output')
    parser.add_option('-v', dest='verbose', action='store_true')
    opts, args = parser.parse_args()
    process(args, output=opts.output, verbose=opts.verbose)

A roughly equivalent command line interface for this case can also be produced by using the argparse module:

import argparse

if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('-o', '--output')
    parser.add_argument('-v', dest='verbose', action='store_true')
    parser.add_argument('rest', nargs='*')
    args = parser.parse_args()
    process(args.rest, output=args.output, verbose=args.verbose)

See Choosing an argument parsing library for details on how the argparse version of this code differs in behaviour from the optparse (and getopt) version.

Ver también

Module optparse

Declarative command line option parsing.

Módulo argparse

More opinionated command line option and argument parsing library.