How to understand it if it's not in python? How to define a function test () to return bool value and then if not test () to understand this statement?

Everyone said the same thing.

The 1.if statement is used to test the condition. If the condition is true, we run a statement (called if- block), otherwise we process it.

Another statement (called else- block) The else clause is optional. -python concise tutorial

2.test () is true, not test () is false, if not, test () will not be executed.

Test () is false and not test () is true. At this point, if not test () can be executed, what will happen next.