CODEWITHSUNDEEP
pythonpython-3.xfilterlambda
thuc dat
thuc dat

Reputation: 21

Unexpected result from lambda

I executed the following:

filter(lambda x: x%2 , range(10))
sum(filter(lambda x: x%2 , range(10)))
abc = filter(lambda x: x%2 , range(10))

sum(abc)    # => 25
sum(abc)    # => 0

Why?

Upvotes: 2

Views: 46

Answers (1)

thefourtheye
thefourtheye

Reputation: 239693

I think you are using Python 3.x. In Python 3.x, filter returns an iterable, not a list.

So, once you iterate the filter with the sum the first time, the filter iterable is exhausted. Next time, when you do the same, filter is already exhausted (it has no more elements). That is why you are getting the default return value 0.

You can confirm the same, like this

>>> abc = filter(lambda x: x%2 , range(10))
>>> list(abc)
[1, 3, 5, 7, 9]
>>> list(abc)
[]

Upvotes: 2

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