list_contains.py

from timeit import timeit

random_list = '''
from random import randint

l = [randint(0, 1000) for _ in range(1000000)]
value = 50
'''

loop = '''
def loop(l):
    for a in l:
        if a == value:
            return True
'''

contain = '''
def contain(l):
    return value in l
'''

set_contain = '''
def set_contain(l):
    return value in set(l)
'''

print('loop', timeit('loop(l)', number=50, setup=random_list + loop))
print('contain', timeit('contain(l)', number=50, setup=random_list + contain))
print('set', timeit('set_contain(l)', number=50, setup=random_list + set_contain))