In other programming languages, like JavaScript, it returns a returns a new array from an original array based instructions you give it. It works similarly in Python, only the list isn't return. It iterates through a list and applies changes you've specified using a function to each element in the list, or multiple lists. I hope this helps some.

I think it is better to train yourself to be a oneliner. Actually I am new here. It is my second day here. And I am trying my best to complete challenges with one line only. It is fun you know. And it changes your mind a lot. THANK YOU ONE LINERS. You teach me a lot.

here are few examples to simplify it:
map(int, a) --> apply int to every list object in list a to make them integers
map(str, a) --> apply str to every list object in list a to make them strings

Everytime.

what's wrong about this solution and which would be best practice in this case?

it applies function to all instance of a

i agreed with you