Complexity of len() with regard to sets and lists

Question

The complexity of len() with regards to sets and lists is equally O(1). How come it takes more time to process sets?

~$ python -m timeit \"a=[1,2,3,         


        

Answer 1

Use this with the -s flag to timeit without taking into account the first string:

~$ python -mtimeit -s "a=range(1000);" "len(a)"
10000000 loops, best of 3: 0.0424 usec per loop
                           ↑ 

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~$ python -mtimeit -s "a={i for i in range(1000)};" "len(a)"
10000000 loops, best of 3: 0.0423 usec per loop
                           ↑ 

Now it's only considering only the len function, and the results are pretty much the same since we didn't take into account the creation time of the set/list.