Op 23-06-16 om 11:53 schreef Marko Rauhamaa:
> Antoon Pardon <antoon.par...@rece.vub.ac.be>:
>
>> Op 23-06-16 om 11:10 schreef Marko Rauhamaa:
>>> The __len__ method is not guaranteed to execute in O(1). See:
>>>
>>> <URL: https://docs.python.org/3/reference/datamodel.html?highlig
>>> ht=__len__#object.__len__>
>> As far as I can see, neither is the __bool__ method.
> Correct, but in the absence of an __empty__ method, __bool__ gives the
> class the best opportunity to check for emptiness quickly.
>
> This is not only a theoretical concern. It's quite common for data
> structures not to maintain an element count because it's extra baggage
> that's not always needed and any application could keep a track of.
> However, an emptiness check is often trivial.
Maybe something like this:
def empty(sq):
try:
iter(sq).next()
except StopIteration:
return False
except:
raise TypeError
else:
return True
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