Simplifying for loop in Python

Question

I have a code snippet like this in Python:

#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")

I want to change the nested for loops into something simpler; what can I do?

BrokenBenchmark · Accepted Answer · 2022-03-14 21:10:34Z

2

Use itertools.product() with the repeat parameter to reduce the amount of nesting:

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")

You can generalize this for lists of size greater than 4 by doing the following:

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")

edited Mar 14, 2022 at 21:10

answered Mar 13, 2022 at 23:27

BrokenBenchmark

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2 Comments

Daxan Over a year ago

Thants for the answer, but I have another question. What happen if de "repeat" it is a variable too? I can code "repeat=x" but, how i do the assignments then?

BrokenBenchmark Over a year ago

Edited answer. Let me know if you have any other questions.

Kelly Bundy · Accepted Answer · 2022-03-13 23:57:31Z

0

A few ways, some using 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")

edited Mar 13, 2022 at 23:57

answered Mar 13, 2022 at 23:49

Kelly Bundy

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2 Comments

Daxan Over a year ago

Thanks !!!, the code works fine, but I forgot to say that the repeat its a variable too, so, how can I get the assignements?

Kelly Bundy Over a year ago

@Daxan Just replace 4 with your variable?

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