CODEWITHSUNDEEP
pythonpython-3.xlistset
user8060120
user8060120

Reputation:

Python concatenate SET or LIST

I try to test two to get set from list:

In first from each list create set and then union to result set or create one list and the return the set of list.

My result looks like no matter in which way to use, is it so? Or I have error logic in my research, or may be exist best way for such union?

import time


def set_from_set(*args):
    l = set()
    return set().union(*args)


def set_from_list(*args):
    l = []
    for larg in args:
        l += larg
    return set(l)


l1 = [x for x in range(1000000)]
l2 = [x for x in range(1000000)]
l3 = [x for x in range(1000000)]
dl1, dl2 = 0, 0

for x in range(100):
    start = time.time()
    set_from_list(l1, l2, l3)
    dl1 += time.time() - start


for x in range(100):
    start = time.time()
    set_from_set(l1, l2, l3)
    dl2 += time.time() - start


print(dl1, dl2)

result:

19.815733194351196 16.40732741355896

Upvotes: 0

Views: 5099

Answers (1)

Nathan Hinchey
Nathan Hinchey

Reputation: 1201

Your problem lies in this function

def set_from_set(*args):
     l= set()
     for larg in args:
         l.union(set(larg))
     return l

the .union() function returns a new set, it doesn't modify your old set in place.

Upvotes: 2

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