[Python-Dev] Python 2.7b1 and argparse's version action (original) (raw)

Tobias Herp Tobias.Herp at gmx.de
Sun Apr 18 15:51:00 CEST 2010

Ben Finney schrieb:

Nick Coghlan <ncoghlan at gmail.com> writes:

I would be a lot happier if argparse as a standard library module just followed optparse's lead here (i.e. defined '--version' only and punted on the shorthand form).

To deal with this in a backwards compatible way while remaining on the path to more conventional behaviour, I suggest the following: 1. For Python 2.7, deprecate just the "-v" default behaviour for the version. This means "--version" and "-v" will be set to invoke different actions when the version argument is supplied (the latter will trigger a deprecation warning if supplied, while the former will work normally). 2. For Python 3.2, don't create the "-v" shorthand at all (i.e. only create "--version"). +1 As someone who uses the existing ‘optparse’ behaviour to implement a number of Unix command-line programs, the above all makes more sense for ‘argparse’ in the standard library if we're expecting it to be a smooth upgrade.

Guys, thanks for your feedback.

Let me see; the suggestion involves the '-v' being set in Python 2.7 by default, but to another action, which yields a DeprecationWarning /and/ performs the version action, right?

The drawback would be: The '-v' wouldn't be available for other uses. But I use it all the time (for verbosity).

I don't see why we shouldn't drop the '-v' altogether; where Python standard libraries are concerned, argparse is a new module, and no compatibility can be broken; people will expect this to follow the optparse habits.

Programs developed against former versions of argparse will continue to work, too; there will just not be a (non-standard) short option generated, but the long option '--version' will be still there. Honestly, how frequently do you query program versions?

Unfortunately adding a new '-V' default action /could/ break existing programs, since people might have worked around the former default; thus we couldn't do this.

Let's get rid of the default '-v' /now/. This is clean, this is easy, it won't break anything (with the possible exception of "prog -v" version output parsers who deserve no better), and we would be done with it.

-- Tobias

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