At 01:39 PM 6/26/2011, Shashank Singh wrote:
On Sun, Jun 26, 2011 at 11:58 PM, Marc Aymerich <glicer...@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 = []
See reference manual section 7.6 "Function definitions" under the
discussion subtitle "Default parameter values are evaluated when the
function definition is executed. "
http://docs.python.org/reference/compound_stmts.html#function-definitions
Yes, this is discussed in many places and many times, but why isn't
it in the Python FAQ? Amazing, yes?
--
Regards
Shashank Singh
http://rationalpie.wordpress.com
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