Don't do micro-optimizations on places where it doesn't matter!

Lol.......

String concatenation is bad when you use it in long recursive functions or loops because, string being immutables, at each step of the concatenation you create 2 strings objects in the heap space (memory). But here, adding just 2 strings together, this is bullshit to say that this is not best practice...

Other ways to do the concatenation:

• ''.join(list of strings elements) for unknown or long lists of strings
• "{}{}{}".format(a,b,c) for short and known number of strings elements

Could you explain why is that?

String concatenation with + is never best practice in Python.