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After recent change (78307 '#13922: argparse no longer incorrectly strips '--' after the first one.'), parse_args stopped working with a tuple
argument. It is easy to pass tuple to argparse by using positional function arguments:
def f(*args):
 parser.parse_args(args)
This will fail, because args is a tuple.
It is necessary to have at least one positional argument to trigger the bug.

I wonder if this is problematic enough that it should be treated as a regression and fixed in the next RC?

On Sun, Sep 02, 2012 at 02:42:34PM +0000, R. David Murray wrote:
> 
> R. David Murray added the comment:
> 
> I wonder if this is problematic enough that it should be treated as a regression and fixed in the next RC?
I believe yes, because I've already hit it in two different projects.
It is also causes susceptible programs to fail completely.
Zbyszek

Let's see what Georg thinks.

The fix looks about right to me.
There's a bug in the tests though:
 parser.parse_args(('x'))
should probably be:
 parser.parse_args(('x',))
since I assume the intent was to test tuples.

Thanks for noticing. Replaced patch with the ('x') -> ('x',) bugfix.

I agree this is a regression and should be fixed.

Committed in release clone as 8c2e87aeb707. Please apply to the main branches as usual.

New changeset 5d8454fcc629 by R David Murray in branch '3.2':
#15847: allow args to be a tuple in parse_args
http://hg.python.org/cpython/rev/5d8454fcc629
New changeset 76655483c5c8 by R David Murray in branch 'default':
merge #15847: allow args to be a tuple in parse_args
http://hg.python.org/cpython/rev/76655483c5c8
New changeset a2147bbf7868 by R David Murray in branch '2.7':
#15847: allow args to be a tuple in parse_args
http://hg.python.org/cpython/rev/a2147bbf7868 

Thanks, Zbyszek. I'm glad you caught this.