Bart Ogryczak a écrit :
> On 2008-01-18, citizen Zbigniew Braniecki testified:
(snip usual default mutable list arg problem)
>> class A():
>>
>> def add (self, el):
>> self.lst.extend(el)
>>
>> def __init__ (self, val=[]):
>> print val
>> self.lst = val
>
> What you want probably is:
> def __init__ (self, val=None):
> if(val == None):
Better to use an identity test here - there's only one instance of the
None object, and identity test is faster than equality test (one
function call faster IIRC !-). Also, the parens are totallu useless.
if val is None:
> self.lst = []
> else:
> from copy import copy
> ### see also deepcopy
> self.lst = copy(val)
What makes you think the OP wants a copy ?
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