Why is a global variable not accessible from a function?

Please tell me why the function does not output the value of s to the console

s = ""I'm global variable""def foo():    print(s)    s = 'Reset global variable'foo()

I assumed that when the interpreter reaches the line print(s), it would understand that there is no such variable in the scope of the foo function. Consequently, it would start looking for it in the outer scope, where it exists.

However, as a result, the following error message is displayed in the console:

Traceback (most recent call last):  File ""index.py"", line 7, in     foo()  File ""index.py"", line 4, in foo    print(s)UnboundLocalError: local variable 's' referenced before assignment

Why does this happen? After all, the variable s is not defined inside the function, so it should be taken from the global scope.