CODEWITHSUNDEEP
pythonperformancetimeit
user1505497
user1505497

Reputation: 329

Speed difference in similar code in Python

I have these 3 functions:

def is_compatible(values):
    supported_types = [(str, unicode), (int, long)]
    for allowed_types in supported_types:
        if isinstance(values[0], allowed_types):
            return all(isinstance(item, allowed_types) for item in values)
    return False


def is_compatible2(values):
    supported_types = [(str, unicode), (int, long)]
    for allowed_types in supported_types:
        if all(isinstance(item, allowed_types) for item in values):
            return True
    return False


def is_compatible3(values):
    supported_types = [(str, unicode), (int, long)]
    return any(
            all(isinstance(item, allowed_types) for item in values) for
            allowed_types in supported_types
        )

Can someone please explain to me, why when I run them with [1,2,3,4,5] as arg in timetit, results are 2.47, 3.07 and 3.94? So the first one is fastest and last one slowst. I simply cannot see any reason for these speed differences. Thanks.

Upvotes: 3

Views: 305

Answers (1)

Joel
Joel

Reputation: 23827

Your answer appears to be here: Why is Python's 'all' function so slow?

Setting up the iterator in all takes time.

In your first function you only do this once. In your second function you occasionally do this twice. So first beats second.

Your second beats third for the same reason again. There's more overhead to set up. A call to any wrapped around the for allowed_types in ... is more overhead than simply for allowed_types in ....

Upvotes: 2

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