gistfile1.py

import threading
import time
from contextlib import contextmanager


@contextmanager
def timeit(exception=Exception):
    start = time.time()
    yield
    print(time.time() - start)


def lf(lst):
    with timeit():
        for i in range(1000):
            lst.append(i)

def f1():
    lst = []
    lf(lst)
    lf(lst)
 
def f2():
    lst = []
    lf(lst)
    t = threading.Thread(target=lf, args=(lst,))
    t.start()
    t.join()
 
def main():
    f1()
    f2()
 
if __name__ == '__main__':
    main()