Re: [Qemu-devel] [PATCH for-2.11 v2 1/5] qmp-shell: Use optparse module

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Aug 15, 2017 at 10:56:07AM +0100, Daniel P. Berrange wrote:
> On Tue, Aug 15, 2017 at 11:47:28AM +0200, Markus Armbruster wrote:
> > Eduardo Habkost <ehabkost@redhat.com> writes:
> > 
> > > It makes command-line parsing and generation of help text much
> > > simpler.
> > 
> > There's really no excuse for parsing command line arguments by hand in
> > Python.
> > 
> > > The optparse module is deprecated since Python 2.7, but argparse
> > > is not available in Python 2.6 (the minimum Python version
> > > required for building QEMU).
> > 
> > We have a few uses of argparse in the tree.  Are they okay?
> > 
> > We also use getopt in places.  Perhaps we should pick one way to parse
> > command lines and stick to it.
> 
> I just came up against this problem with keycodemapdb which I'm adding as
> a submodule to qemu.  I used argparse there because it is the modern
> recommended API for python >= 2.7.   I examined possibilty of using
> optparse instead, but it lacks key features - in particular the idea
> of 'subcommands' is entirely missing from optparse.
> 
> The 'argparse' module is part of python core, but is *also* available
> as a standalone module that is implemented in terms of optparse.
> 
> So, I would suggest that we just copy the 'argparse' module into the
> QEMU 'scripts/thirdparty' directory.
> 
> Then in any files which need argparse, you can do this
> 
>   try:
>       import argparse
>   except:
>       import os, sys
>       sys.path.append(os.path.join(os.path.dirname(__file__), "thirdparty"))
>       import argparse

What about:

  try:
      import argparse
  except:
      from thirdparty import argparse

(I think we could move all our Python modules [qemu.py, qmp.py]
to ./scripts/qemu/, so this would become "qemu.thirdparty").

> 
> so that it tries to use the argparse provided by python, and falls back
> to pulling in the one in our scripts/thirdparty directory.
> 
> When we finally bump our min python to 2.7, we can simply drop this
> compat code for the import statement.  This avoids need for us to
> re-write code to use a deprecated API, with a worse feature set.

Sounds good to me.

-- 
Eduardo