Python optparse metavar

Question

Hi, I am not sure what optparse's metavar parameter is used for. I see it used all around, but I can't see its use.

Can someone make it clear to me? Thanks.

Answer 1

metavar seems to be used for generating help : http://www.python.org/doc/2.5.2/lib/optparse-generating-help.html

Answer 2

As @Guillaume says, it's used for generating help. If you want to have an option that takes an argument, such as a filename, you can add the metavar parameter to the add_option call so your preferred argument name/descriptor is output in the help message. From the current module documentation:

usage = "usage: %prog [options] arg1 arg2"
parser = OptionParser(usage=usage)
parser.add_option("-f", "--filename",
                  metavar="FILE", help="write output to FILE"),

would produce help like this:

usage: <yourscript> [options] arg1 arg2

options:
  -f FILE, --filename=FILE

The "FILE" after the "-f" and the "--filename" comes from the metavar.

Answer 3

metavar is var used for print in the screen after option . usually use for suggestion input after option are there FILE or INT or STRING to user without metavar optparse will print dest value after option you've been added