variable & scoping question.

[MRAB]

Francesco Bochicchio wrote:
> On Aug 10, 5:12 pm, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
>> Cornelius Keller wrote:
>>> Hi,
>>> I'm a quite fresh python programmer, (6 Month python experience).
>>> Today I found something I absolotly don'nt understand:
>>> given the following function:
>>> def test_effect(class_id=None,class_ids=[]):
>>>     if class_id is not None:
>>>         if class_id not in class_ids:
>>>             class_ids.append(int(class_id))
>>>     print class_ids
>>> I observe that the class_ids array is growing when it is called with
>>> different class id's.
>>> I expected class_ids to be [] if the keyword argument is not set, but
>>> it seems to beahve like a static variable if not set.
>> http://effbot.org/zone/default-values.htm
>>
>> Diez
> 
> Maybe on the first page of python.org there should be a 'python
> gotchas' link to a page listing these few
> non-intuituive peculiarities of our beloved snake ... same goes for
> the official python tutorial ...
> 
Should they be called 'snake bites'? Well, pythons are constrictors, not
biters, but if Python is being non-intuitive... :-)