Swap cases in a string

Question

I\'m trying to solve this challenge in hackerrank, which asks to convert all lowercase letters to uppercase letters and vice versa.

I attempt it with the following code:

Answer 1

As @Julien stated in comment upper and lower methods return a copy, and do not change the object itself. See this docs.

EDIT @aryamccarthy reminded me of already existing feature for this kind of task in python: swapcase() method. See more here. Note this also returns a copy of the string.