How to reduce on a list of tuples in python

Question

I have an array and I want to count the occurrence of each item in the array.

I have managed to use a map function to produce a list of tuples.

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Answer 1

You could use Counter:

from collections import Counter
arr = [11817685, 2014036792, 2014047115, 11817685]
counter = Counter(arr)
print zip(counter.keys(), counter.values())

EDIT:

As pointed by @ShadowRanger Counter has items() method:

from collections import Counter
arr = [11817685, 2014036792, 2014047115, 11817685]
print Counter(arr).items()