getopt
--- 用於命令列選項的 C 風格剖析器¶原始碼:Lib/getopt.py
備註
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 選擇一個命令列參數剖析函式庫 for
additional details.
這個模組提供兩個函式和一個例外:
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).
備註
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 --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.
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 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.
為了向後相容性而設的 GetoptError
別名。
一個僅使用 Unix 風格選項的範例:
>>> 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']
使用長選項名稱同樣容易:
>>> 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']
在腳本中,典型的用法如下:
import getopt, sys
def main():
try:
opts, args = getopt.getopt(sys.argv[1:], "ho:v", ["help", "output="])
except getopt.GetoptError as err:
# 印出幫助訊息並退出:
print(err) # 會印出像是 "option -a not recognized" 的訊息
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)
參見 選擇一個命令列參數剖析函式庫 以瞭解這段程式碼的 argparse
版本與 optparse
(以及 getopt
)版本在行為上的差異。