Python Variable Scope

Variable has scope, and exist precedence regarding the local of reading values (local then global)
If you want to read global variables with variable local with the same name is possible to use global <variable name>. Example below:

>>> b = 6
>>> def f3(a):
...     global b
...     print(a)
...     print(b)
...     b = 9
...
>>> f3(3)
3
6
>>> b
9

Logic Lookup

There is a global x declaration, x comes from and is assigned to the x global variable module.
There is a non-local x declaration, x comes from and is assigned to the x local variable of the nearest surrounding function where x is defined.
x is a parameter or is assigned a value in the function body, then x is the local variable.
If x is referenced but is not assigned and is not a parameter:
- x will be looked up in the local scopes of the surrounding function bodies (non-local scopes).
- If not found in surrounding scopes, it will be read from the module global scope.
- If not found in the global scope, it will be read from __builtins__.__dict__