How to replace indexes by values from different list?

Question

I have two lists:

test_list1 = [2, 3, 4, 5, 2, 4] 
test_list2 = [[1, 5], [4, 2, 3], [0]]

I want to replace the indexes in test_list2 by the values in test_list1 such that the result would be:

[[3, 4], [2, 4, 5], [2]]

I have tried this:

res = [test_list1[idx] for idx in test_list2]

I have notice that my code only works for a list without sublists

Answer 1

You can use a recursive function. This will go through an arbitarily nested list, replacing the values.

def replace(lst, replacements):
    for i, val in enumerate(lst):
        if isinstance(val, list):
            replace(val, replacements)
        else:
            lst[i] = replacements[val]

            
test_list1 = [2, 3, 4, 5, 2, 4]
test_list2 = [[1, 5], [4, 2, 3], [0]]

replace(test_list2, test_list1)
print(test_list2)

Gives:

[[3, 4], [2, 4, 5], [2]]

Answer 2

A oneliner with list comprehension and map function could look like this:

test_list1 = [2, 3, 4, 5, 2, 4]
test_list2 = [[1, 5], [4, 2, 3], [0]]

output = list(map(lambda x: [test_list1[y] for y in x], test_list2))

print(output)
# [[3, 4], [2, 4, 5], [2]]