Question

I have a number of lists that I’m going to use in my program, but I need to be sure that they are all the same length, or I’m going to get problems later on in my code.

What’s the best way to do this in Python?

For example, if I have three lists:

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

I could do something like:

l = [len(a), len(b), len(c)]
if max(l) == min(l):
   # They're the same

Is there a better or more Pythonic way to do this?

Answer 1

Assuming you have a non-empty list of lists, e.g.

my_list = [[1, 2, 3], ['a', 'b'], [5, 6, 7]]

you could use

n = len(my_list[0])
if all(len(x) == n for x in my_list):
    # whatever

This will short-circuit, so it will stop checking when the first list with a wrong length is encountered.