Python optparse: how to make a repeatable group of options?

Question

Here is a simplified view of the script I am programming in python:

• The script is used to compare two files.
• The type (local or remote) of each file must be specified (mandatory)

• For a local file:

  • Its filename must be specified (mandatory)
  • Its path can be specified (optional, default is .)

• For a remote file:

  • Its filename must be specified (mandatory)
  • Its path must be specified (mandatory)
  • An boolean flag can be specified (optional)

So I would like to use it like this:

compare.py -L local.txt -L local2.txt -p /tmp/

or

compare.py -L local.txt -R remote.txt -p remoteDir/ --myFlag

So I need to define 2 groups of options (local/L and remote/R), each containing its own set of mandatory and optional options.

I have not found a way to achieve this with optparse (or even argparse, but I'd like to stick with optparse if possible as I'm writing the script for Python 2.6.7)

Is there any clean solution ?

Answer 1

I would do it with option callbacks + helper object which traces context of the current option. Example:

from optparse import OptionParser

class FileBase(object):
    def __init__(self, fname):
        self.fname = fname
        self.path = None
class LocalFile(FileBase):
    pass
class RemoteFile(FileBase):
    pass

class FileOptionParser(object):
    def __init__(self):
        self.last_file = None
        self.files = []

    def set_path(self, option, opt, value, parser):
        self.last_file.path = value

    def set_file(self, option, opt, value, parser):
        if   option.dest=="local" : cls = LocalFile
        elif option.dest=="remote": cls = RemoteFile
        else:                       assert False
        self.last_file = cls(value)
        self.files.append(self.last_file)
        setattr(parser.values, option.dest, self.last_file)

fop = FileOptionParser()

parser = OptionParser()
parser.add_option('-L', '--local',  type='string', action='callback', callback=fop.set_file)
parser.add_option('-R', '--remote', type='string', action='callback', callback=fop.set_file)
parser.add_option('-p', '--path',   type='string', action='callback', callback=fop.set_path)

(options, args) = parser.parse_args()
print [(f.fname, f.path) for f in fop.files]

example is:

> python test.py -L local.txt -R remote.txt -p remoteDir/
[('local.txt', None), ('remote.txt', 'remoteDir/')]