Why does the third part of this code don't work?

Question

https://code.sololearn.com/cXOLg2IZuriC/?ref=app

Answer 1

If you want to modify a variable var inside the function you need either to use a local variable, or to use a global var statement. Since you modify var3 python assumes it is local, and not the global var3. And it cant print it.

Answer 2

Error message says it all:
local variable 'var3' referenced before assignment

Switch lines 34 and 35.

Answer 3

Yes, I know it, but why I can't reference it? (the other two codes are similar)

Answer 4

Thanks!