Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: <c.buhtz@posteo.jp>
Newsgroups: comp.lang.python
Subject: [argparse] optional parameter without --switch
Date: Mon, 23 Nov 2015 18:04:01 +0100
Lines: 32
Message-ID: <mailman.88.1448345018.2291.python-list@python.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-Trace: news.uni-berlin.de Mdtm28M2ado+f8qqLc4YJwqi6Ldl3XMO0TDGSEvlkgPQ==
Return-Path: <c.buhtz@posteo.jp>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'python3': 0.05; 'sys': 0.05; 'that?': 0.05; 'namespace': 0.09; 'optional': 0.09; 'received:172.16.0': 0.09; 'skip:# 30': 0.09; 'python': 0.10; 'skip:# 20': 0.13; 'argparse': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'subject:argparse': 0.16; 'subject:] ': 0.19; 'fix': 0.21; '(on': 0.22; 'arguments': 0.22; 'parameter': 0.22; 'parser': 0.22; '(like': 0.23; 'skip:l 40': 0.23; 'import': 0.24; 'script': 0.25; 'skip:# 10': 0.27; 'switch': 0.27; 'optional.': 0.29; 'error.': 0.31; 'but': 0.36; 'should': 0.36; 'there': 0.36; 'to:addr:python-list': 0.36; 'two': 0.37; 'charset :us-ascii': 0.37; 'means': 0.39; 'subject:[': 0.39; 'test': 0.39; 'to:addr:python.org': 0.40; 'received:de': 0.40; 'from:no real name:2**0': 0.60; 'header:Message-Id:1': 0.61; 'skip:a 40': 0.64; 'received:185': 0.91
X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.23; i686-pc-linux-gnu)
X-Mailman-Approved-At: Tue, 24 Nov 2015 01:03:37 -0500
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.20+
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Xref: csiph.com comp.lang.python:99297

I want to call (on bash) a Python script in this two ways without any
error.

    ./arg.py
    ./arg.py TEST

It means that the parameter (here with the value `TEST`) should be
optional. With argparse I only know a way to create optional paramters
when they have a switch (like `--name`).

Is there a way to fix that?

    #!/usr/bin/env python3    
    import sys
    import argparse

    parser = argparse.ArgumentParser(description=__file__)
    
    # must have
    #parser.add_argument('name', metavar='NAME', type=str)
    
    # optional BUT with a switch I don't want
    #parser.add_argument('--name', metavar='NAME', type=str)
    
    # store all arguments in objects/variables of the local namespace
    locals().update(vars(parser.parse_args()))
    
    print(name)
    
    sys.exit()
-- 
GnuPGP-Key ID 0751A8EC