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Re: Default value for optional parameters unexpected behaviour?

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On Sun, Jun 26, 2011 at 11:58 PM, Marc Aymerich <glicerinu@gmail.com> wrote:
> Hi,
> I'm trying to define a function that has an optional parameter which
> should be an empty list whenever it isn't given. However, it takes as
> value the same value as the last time the function was executed. What
> is the reason of this behaviour? How does python deal with default
> values (i.e. when are they assigned/created)?

This has been discussed before in this list, quite a few times
http://mail.python.org/pipermail/python-list/2010-March/1239044.html

A solution is to accept default value as None assign to [] by checking
for None inside the function

def f(a=None):
  if a is None: a = []



-- 
Regards
Shashank Singh
http://rationalpie.wordpress.com

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Default value for optional parameters unexpected behaviour? Marc Aymerich <glicerinu@gmail.com> - 2011-06-26 11:28 -0700
  Re: Default value for optional parameters unexpected behaviour? Shashank Singh <shashank.sunny.singh@gmail.com> - 2011-06-27 00:09 +0530
  Re: Default value for optional parameters unexpected behaviour? Corey Richardson <kb1pkl@aim.com> - 2011-06-26 14:36 -0400
  Re: Default value for optional parameters unexpected behaviour? Noah Hall <enalicho@gmail.com> - 2011-06-26 19:45 +0100
  Re: Default value for optional parameters unexpected behaviour? Terry Reedy <tjreedy@udel.edu> - 2011-06-26 14:46 -0400
  Re: Default value for optional parameters unexpected behaviour? Benjamin Kaplan <benjamin.kaplan@case.edu> - 2011-06-26 12:21 -0700
  Re: Default value for optional parameters unexpected behaviour? Corey Richardson <kb1pkl@aim.com> - 2011-06-26 15:23 -0400

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