what error "indentation error:expected an indentation block mean"?

Question

error appear when write code by python

Answer 1

Python uses indentation to define blocks. For example, to show which
statements are controlled by a for or if statement, the controlled
statements are indented.

So when typing these examples you need to indent the lines after the
for, if or while. The indentation can be any consistent white space.
Four spaces is a very common indent. When typing at the interactive
prompt I usually use two spaces just because it's easier to type.

Answer 2

@Sanga Raoul, i think that's 4 spaces else you have got an error