timing_array_accessing.py

import timeit
import random
import array

setups = """xs = array('i', [0]) * n #array
xs = [0] * n #list
"""
# xs = [None] * n #list
#       ^^^^ make no difference in timing

stmts = """for i in indices: xs[i] #rand read
for i in indices: xs[i] = i        #rand write
for i in range(n): xs[i]     #seq read
for i in range(n)[::-1]: xs[i]     #seq read (rev)
for i in range(n): xs[i] = i #seq write
for i in range(n)[::-1]: xs[i] = i #seq write (rev)
"""

n = 10 ** 6
# n = int(2e5)
indices = [*range(n)]
random.shuffle(indices)
ts = []
for ln in stmts.splitlines():
    stmt, tag = ln.split('#')
    print(tag)
    for ln in setups.splitlines():
        setup, _tag = ln.split('#')
        k, t = timeit.Timer(stmt,
            setup=setup,
            globals=dict(n=n, indices=indices, array=array.array)
            ).autorange()
        t /= k
        ts.append(t)
        print(f'{t*1000: 7.1f} ms : {_tag}')
    print(f'{ts[-2]/ts[-1]*100: 7.1f}%\n')