from time import perf_counter
from random import shuffle


for L in 10, 100, 1000, 5000, 10000, 50000, 100000, 200000:
    a = [1] * L
    idx = list(range(len(a)))
    shuffle(idx)
    start = perf_counter()              # turn-on chronometer
    for k in range(L):
        a.append(3)
    fast_end = perf_counter() - start   # measure time from start
    start = perf_counter()
    for k in range(L):
        a.insert(idx[k], 3)
    slow_end = perf_counter() - start
    print(f"Length = {L:6}: fast append {fast_end:6.3f}, slow insert {slow_end:6.3f}")