1:mod:`getopt` --- C-style parser for command line options 2========================================================= 3 4.. module:: getopt 5 :synopsis: Portable parser for command line options; support both short and long option 6 names. 7 8**Source code:** :source:`Lib/getopt.py` 9 10-------------- 11 12.. note:: 13 14 The :mod:`getopt` module is a parser for command line options whose API is 15 designed to be familiar to users of the C :c:func:`getopt` function. Users who 16 are unfamiliar with the C :c:func:`getopt` function or who would like to write 17 less code and get better help and error messages should consider using the 18 :mod:`argparse` module instead. 19 20This module helps scripts to parse the command line arguments in ``sys.argv``. 21It supports the same conventions as the Unix :c:func:`getopt` function (including 22the special meanings of arguments of the form '``-``' and '``--``'). Long 23options similar to those supported by GNU software may be used as well via an 24optional third argument. 25 26This module provides two functions and an 27exception: 28 29 30.. function:: getopt(args, options[, long_options]) 31 32 Parses command line options and parameter list. *args* is the argument list to 33 be parsed, without the leading reference to the running program. Typically, this 34 means ``sys.argv[1:]``. *options* is the string of option letters that the 35 script wants to recognize, with options that require an argument followed by a 36 colon (``':'``; i.e., the same format that Unix :c:func:`getopt` uses). 37 38 .. note:: 39 40 Unlike GNU :c:func:`getopt`, after a non-option argument, all further 41 arguments are considered also non-options. This is similar to the way 42 non-GNU Unix systems work. 43 44 *long_options*, if specified, must be a list of strings with the names of the 45 long options which should be supported. The leading ``'--'`` 46 characters should not be included in the option name. Long options which 47 require an argument should be followed by an equal sign (``'='``). Optional 48 arguments are not supported. To accept only long options, *options* should 49 be an empty string. Long options on the command line can be recognized so 50 long as they provide a prefix of the option name that matches exactly one of 51 the accepted options. For example, if *long_options* is ``['foo', 'frob']``, 52 the option ``--fo`` will match as ``--foo``, but ``--f`` 53 will not match uniquely, so :exc:`GetoptError` will be raised. 54 55 The return value consists of two elements: the first is a list of ``(option, 56 value)`` pairs; the second is the list of program arguments left after the 57 option list was stripped (this is a trailing slice of *args*). Each 58 option-and-value pair returned has the option as its first element, prefixed 59 with a hyphen for short options (e.g., ``'-x'``) or two hyphens for long 60 options (e.g., ``'--long-option'``), and the option argument as its 61 second element, or an empty string if the option has no argument. The 62 options occur in the list in the same order in which they were found, thus 63 allowing multiple occurrences. Long and short options may be mixed. 64 65 66.. function:: gnu_getopt(args, options[, long_options]) 67 68 This function works like :func:`getopt`, except that GNU style scanning mode is 69 used by default. This means that option and non-option arguments may be 70 intermixed. The :func:`getopt` function stops processing options as soon as a 71 non-option argument is encountered. 72 73 If the first character of the option string is ``'+'``, or if the environment 74 variable :envvar:`POSIXLY_CORRECT` is set, then option processing stops as 75 soon as a non-option argument is encountered. 76 77 .. versionadded:: 2.3 78 79 80.. exception:: GetoptError 81 82 This is raised when an unrecognized option is found in the argument list or when 83 an option requiring an argument is given none. The argument to the exception is 84 a string indicating the cause of the error. For long options, an argument given 85 to an option which does not require one will also cause this exception to be 86 raised. The attributes :attr:`msg` and :attr:`opt` give the error message and 87 related option; if there is no specific option to which the exception relates, 88 :attr:`opt` is an empty string. 89 90 .. versionchanged:: 1.6 91 Introduced :exc:`GetoptError` as a synonym for :exc:`error`. 92 93 94.. exception:: error 95 96 Alias for :exc:`GetoptError`; for backward compatibility. 97 98An example using only Unix style options: 99 100 >>> import getopt 101 >>> args = '-a -b -cfoo -d bar a1 a2'.split() 102 >>> args 103 ['-a', '-b', '-cfoo', '-d', 'bar', 'a1', 'a2'] 104 >>> optlist, args = getopt.getopt(args, 'abc:d:') 105 >>> optlist 106 [('-a', ''), ('-b', ''), ('-c', 'foo'), ('-d', 'bar')] 107 >>> args 108 ['a1', 'a2'] 109 110Using long option names is equally easy: 111 112 >>> s = '--condition=foo --testing --output-file abc.def -x a1 a2' 113 >>> args = s.split() 114 >>> args 115 ['--condition=foo', '--testing', '--output-file', 'abc.def', '-x', 'a1', 'a2'] 116 >>> optlist, args = getopt.getopt(args, 'x', [ 117 ... 'condition=', 'output-file=', 'testing']) 118 >>> optlist 119 [('--condition', 'foo'), ('--testing', ''), ('--output-file', 'abc.def'), ('-x', '')] 120 >>> args 121 ['a1', 'a2'] 122 123In a script, typical usage is something like this:: 124 125 import getopt, sys 126 127 def main(): 128 try: 129 opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="]) 130 except getopt.GetoptError as err: 131 # print help information and exit: 132 print str(err) # will print something like "option -a not recognized" 133 usage() 134 sys.exit(2) 135 output = None 136 verbose = False 137 for o, a in opts: 138 if o == "-v": 139 verbose = True 140 elif o in ("-h", "--help"): 141 usage() 142 sys.exit() 143 elif o in ("-o", "--output"): 144 output = a 145 else: 146 assert False, "unhandled option" 147 # ... 148 149 if __name__ == "__main__": 150 main() 151 152Note that an equivalent command line interface could be produced with less code 153and more informative help and error messages by using the :mod:`argparse` module:: 154 155 import argparse 156 157 if __name__ == '__main__': 158 parser = argparse.ArgumentParser() 159 parser.add_argument('-o', '--output') 160 parser.add_argument('-v', dest='verbose', action='store_true') 161 args = parser.parse_args() 162 # ... do something with args.output ... 163 # ... do something with args.verbose .. 164 165.. seealso:: 166 167 Module :mod:`argparse` 168 Alternative command line option and argument parsing library. 169 170