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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. This module provides a single
function and an exception:
-
| getopt( |
args, options[, long_options]) |
- 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:]". options 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.
long_options, 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 ("="). To accept only long
options, options 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, it long_options is ['foo', 'frob'],
the option --fo will match as --foo,
but --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.
-
| gnu_getopt( |
args, options[, long_options]) |
- 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.
- exception 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.
Changed in version 1.6: Introduced GetoptError
as a synonym for error.
- exception error
- Alias for GetoptError; for backward compatibility.
An example using only Unix style options:
>>> 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']
Using long option names is equally easy:
>>> 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']
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:
# print help information and exit:
usage()
sys.exit(2)
output = None
verbose = False
for o, a in opts:
if o == "-v":
verbose = True
if o in ("-h", "--help"):
usage()
sys.exit()
if o in ("-o", "--output"):
output = a
# ...
if __name__ == "__main__":
main()
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