Avoiding multiple nested for-loops in python

Question

How to avoid multiple nested for-loops when one nested for-loop has range up to the current iteration of the outer for-loop? For example, consider the following code: This program returns a triplet from a list arr such that arr[i] - arr[j] = arr[j] - arr[k] = d and i<j<k.

d =3
arr = [1, 2, 4, 5, 7, 8, 10]
list1 = []

for biggest in range(0, len(arr)):
    for bigger in range(0, biggest):
        for big in range(0, bigger):
            if abs(arr[big] - arr[bigger]) == d and abs(arr[bigger] - arr[biggest]) == d:
                list1.append([arr[big], arr[bigger], arr[biggest]])
print(list1))

Are there any other alternatives to using multiple nested loops?

Answer 1

You can replace the three loops with:

from itertools import combinations

for big, bigger, biggest in combinations(range(0, len(arr)), 3):

You can replace all the code with:

print([t for t in combinations(arr, 3)
       if t[2] - t[1] == t[1] - t[0] == d])