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This question already has an answer here:

Hey so i was wondering which is the more efficient way, or better practice to do in this situation.

1,

def function():
    global number
    number += 2

Or 2,

def function(number):
    return number += 2

Thanks.

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marked as duplicate by gnat, GlenH7, Bart van Ingen Schenau, amon, Snowman Feb 4 '15 at 5:04

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
6  
Did you try searching? Searching for "python local global performance" turned up this Stack Overflow question as the first result. More importantly, mutable global variables are a bad idea. – Doval Feb 3 '15 at 17:04
    
If you are working on something where the performance difference between a global and a local matters, you should probably not be using python in the first place. This is a micro-optimization at best, and python's reasons for existence don't include speed. – Steven Burnap Feb 4 '15 at 4:25
up vote 2 down vote

Performance is irrelevant. Globals are evil (as gnat mentioned); you are best off forgetting the global keyword exists. There is always a better way.

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