Marc 'BlackJack' Rintsch wrote:
> > def __init__(self,answers={}):
> > self.answers=answers
>
> Default arguments are only evaluated once when the ``def`` is executed,
> so all your `Storage` classes share the same dictionary. One idiom to
> solve this is:
>
> def __init__(self, answers=None):
> self.answers = answers or dict()
Nitpick: the expression 'answers or dict()' is false economy. It may provoke
even subtler errors, because an empty dict is False in a boolean context.
Example:
# here the answers are shared:
shared_answers = {"question": "answer"}
first = Storage(shared_answers)
second = Storage(shared_answers)
print second.answers is first.answers # True
# here the answers aren't shared:"
shared_answers = {}
first = Storage(shared_answers)
second = Storage(shared_answers)
shared_answers["question"] = "answer"
print second.answers is first.answers # False
To avoid the confusion I recommend the following:
def __init__(self, answers=None):
if answers is None:
answers = {}
self.answers = answers
Peter
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