Python for loop vs list comprehension speed test. This is just testing the speed of performing a particular operation in both a for loop and list comprehension. Note that the list comprehension version uses more memory because it is storing the results. This could be partially responsible for it being slower.

for_loop.py

import sys
num = int(sys.argv[1])

def test(i):
    return i+1

for i in range(num):
    t = test(i)

list_comp.py

import sys
num = int(sys.argv[1])

def test(i):
    return i+1

[test(i) for i in range(num)]

results.txt

cmadrigal-MBP:python-loop-test caleb.madrigal$ time python3 list_comp.py 50000000

real	0m10.099s
user	0m8.602s
sys	0m1.484s
cmadrigal-MBP:python-loop-test caleb.madrigal$ time python3 for_loop.py 50000000

real	0m9.281s
user	0m9.227s
sys	0m0.014s