Finding and replacing within a 'grouped' list

Question

Is there a way to do a find and replace for lists that are sorted into groups?

Scenario:

my_list = [[1,5],[3,6],[-1,9]]

I want to replace all the values that are 1 or 3 to be replaced with 11 such that output is:

my_list = [[11,5],[11,6],[-1,9]]

I have been able to do the find replace by creating 3 variables and adding it such that it is one big list however I still want to retain the same form thus I am wondering how to do it while it's still in that form?

Answer 1

The alternative to the list comprehension solution would be modifying the original list with:

for group in my_list:
    for i, x in enumerate(group):
        if x in {1, 3}:
            group[i] = 11

This would be the best option if your lists contain a large number of elements.

Answer 2

You could achieve this with a nested list comprehension such as:

my_list = [[y if y not in [1, 3] else 11 for y in x] for x in my_list]

This retains the nested list structure and replaces any 1 or 3 with 11. Output is:

[[11, 5], [11, 6], [-1, 9]]