import itertools
A = range(1000)
%%timeit
for x in itertools.product(A, A):
pass
30.8 ms ± 910 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for a1, a2 in itertools.product(A, A):
pass
22.8 ms ± 293 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for a1 in A:
for a2 in A:
pass
22.6 ms ± 345 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for x in ((a1, a2) for a1 in A for a2 in A):
pass
82.2 ms ± 467 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for a1, a2 in ((a1, a2) for a1 in A for a2 in A):
pass
91.4 ms ± 276 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
v = 0
for a1, a2 in itertools.product(A, A):
v += a1 * a2
98.8 ms ± 579 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
v = 0
for a1 in A:
for a2 in A:
v += a1 * a2
95.7 ms ± 4.05 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
v = sum(a1 * a2 for a1, a2 in itertools.product(A, A))
94 ms ± 2.36 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
v = sum(a1 * a2 for a1 in A for a2 in A)
92.7 ms ± 4.83 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
B = range(100)
%%timeit
for x in itertools.product(B, B, B):
pass
31.6 ms ± 725 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for b1, b2, b3 in itertools.product(B, B, B):
pass
26.2 ms ± 490 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for b1 in B:
for b2 in B:
for b3 in B:
pass
12.9 ms ± 176 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%%timeit
for x in ((b1, b2, b3) for b1 in B for b2 in B for b3 in B):
pass
80.9 ms ± 1.27 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
%%timeit
for b1, b2, b3 in ((b1, b2, b3) for b1 in B for b2 in B for b3 in B):
pass
93.8 ms ± 3.22 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)