简化 Python 中的 for 循环

Question

我在 Python 中有这样的代码片段：

#list_1 have a previous value that we dont know
n = 40 #This value can change

list_2 = [0, 0, 0, 0]

#We are trying all the values possibles for 4 positions and 40 different numbers

for a in range(n):
    for b in range(n):
        for c in range(n):
            for d in range(n):
                list_2[0] = a
                list_2[1] = b
                list_2[2] = c
                list_2[3] = d
                if list_1 == list_2:
                   print("Ok")

我想将嵌套的 for 循环更改为更简单的东西；我能做什么？

Answer 1

使用itertools.product()和repeat参数来减少嵌套量：

from itertools import product

for a, b, c, d in product(range(n), repeat=4):
    list_2 = [a, b, c, d] # Can condense the assignments into one line as well.
    if list_1 == list_2:
        print("Ok")

您可以通过执行以下操作将此概括为大于 4 的列表：

from itertools import product
x = # length of lists to find matches for
for item in product(range(n), repeat=x):
    list_2 = list(item)
    if list_1 == list_2:
        print("Ok")

Answer 2

一些方法，一些使用 itertools.product...

for [*list_2] in product(range(n), repeat=4):
    if list_1 == list_2:
        print("Ok")

list_2 = []
for list_2[:] in product(range(n), repeat=4):
    if list_1 == list_2:
        print("Ok")

if tuple(list_1) in product(range(n), repeat=4):
    print("Ok")

if list_1 in map(list, product(range(n), repeat=4)):
    print("Ok")

if len(list_1) == 4 and all(x in range(n) for x in list_1):
    print("Ok")

if len(list_1) == 4 and set(list_1) <= set(range(n)):
    print("Ok")

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