pattern = r"(.+) \1"

Question

What exactly it do?

Answer 1

its a regular expression where .+ means one or many dots
and \1 means match the exact same text that was matched by 1st group.

group means written content written in parenthesis( ).

Answer 2

'.+' in regexp means one or many characters ( the dot is the wildcard ).
To match a dot, you need to escape it '\.' or to use it in a class of char: '[.]'...

Answer 3

Thanks