Output of python ?

Question

Output of given program is 10 because a=5 and b=5 in the end but i did not understood why pre decrement does not change the value of a initially to 4 ?
a=5
b=7
if not a!=b-2:
b=--a
print(a+b)

Answer 1

incrementing/decrementing with ++ and — isnt supported in Python

Answer 2

It's not just about not being allowed simultaneously. As Jenny 🖤 said, the ++ and -- operators are not supported in Python.

Answer 3

I got it .. we can not assign and increment/decrement simultaneously.
It is just changing sign of a..like b=-a means a=5 and b=-5 and for b=--a means a=5 and b=-(-5)=5