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.
A more convenient, flexible, and powerful alternative is the
This module provides two functions and an exception:
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 (
':'; i.e., the same format that Unix
getopt() uses).Note 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 (
'='). Optional arguments are not supported. 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
--f will not match uniquely, so
GetoptError will be raised.The return value consists of two elements: the first is a list of
(option, value) pairs; the second is the list of program arguments left after the option list was stripped (this is a trailing slice of args). Each option-and-value pair returned has the option as its first element, prefixed with a hyphen for short options (e.g.,
'-x') or two hyphens for long options (e.g.,
'--long-option'), and the option argument as its second element, or an empty string if the option has no argument. The options occur in the list in the same order in which they were found, thus allowing multiple occurrences. Long and short options may be mixed.
getopt.``gnu_getopt(args, shortopts, longopts=)
This function works like
getopt(), except that GNU style scanning mode is used by default. This means that option and non-option arguments may be intermixed. The
getopt() function stops processing options as soon as a non-option argument is encountered.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.
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
opt give the error message and related option; if there is no specific option to which the exception relates,
opt is an empty string.
GetoptError; for backward compatibility.
An example using only Unix style options:
Using long option names is equally easy:
In a script, typical usage is something like this:
More object-oriented command line option parsing.