"getopt" --- C-style parser for command line options
****************************************************

**ソースコード:** Lib/getopt.py

注釈:

  The "getopt" module is a parser for command line options whose API
  is designed to be familiar to users of the C "getopt()" function.
  Users who are unfamiliar with the C "getopt()" function or who would
  like to write less code and get better help and error messages
  should consider using the "argparse" module instead.

======================================================================

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.

このモジュールは2つの関数と1つの例外を提供しています:

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).

   注釈:

     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.

   返り値は2つの要素から成っています: 最初は "(option, value)" のタプ
   ルのリスト、2つ目はオプションリストを取り除いたあとに残ったプログラ
   ムの引数リストです (*args* の末尾部分のスライスになります)。それぞ
   れの引数と値のタプルの最初の要素は、短形式の時はハイフン 1つで始ま
   る文字列 (例: "'-x'")、長形式の時はハイフン2つで始まる文字列 (例:
   "'--long-option'") となり、引数が2番目の要素になります。引数をとら
   ない場合には空文字列が入ります。オプションは見つかった順に並んでい
   て、複数回同じオプションを指定できます。長形式と短形式のオプション
   は混在できます。

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

   この関数はデフォルトで GNU スタイルのスキャンモードを使う以外は
   "getopt()" と同じように動作します。つまり、オプションとオプションで
   ない引数とを混在させることができます。"getopt()" 関数はオプションで
   ない引数を見つけると解析を停止します。

   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 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

   "GetoptError" へのエイリアスです。後方互換性のために残されています
   。

Unix スタイルのオプションを使った例です:

   >>> 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']

長形式のオプションを使っても同様です:

   >>> 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 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"
       # ...

   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
"argparse" module:

   import argparse

   if __name__ == '__main__':
       parser = argparse.ArgumentParser()
       parser.add_argument('-o', '--output')
       parser.add_argument('-v', dest='verbose', action='store_true')
       args = parser.parse_args()
       # ... do something with args.output ...
       # ... do something with args.verbose ..

参考:

  "argparse" モジュール
     Alternative command line option and argument parsing library.
