Question

I have few lists like:

a = [1, 2, 3, 4, 5]
b = [4, 6, 5, 9, 2]
c = [4, 7, 9, 1, 2]

I want to trim all of them using a loop, instead of doing as below:

a[-2:]
b[-2:]
c[-2:]

I tried but got confused with pass by value or pass by reference fundamentals, looked into other questions as well but no help.

Thanks

Answer 1

for l in [a, b, c]:
    del l[-2:]

This removes the last two elements from each list. If you want to remove all but the last two elements only, do this:

for l in [a, b, c]:
    del l[:-2]

There’s no need to worry about references here; the list over which the for loop iterates contains references to a, b and c, and each list is mutated in-place by deleting a list slice.