What is the logic of this global python chip?

Question

I was messing around with the scope in python and found something that, in my opinion, is rather strange:

g = 5 def foo(a): if a: global g g = 10 else: g = 20 print("global g: ",g) foo(False) print("global g: ",g) # 20?! What? foo(True) print("global g: ",g) 

I believe that the second fingerprint should have been "5", since the global operator has never been executed, but, obviously, the result is 20 (!).

What is the logic behind this?

Answer 1

global keyword is used by the python compiler to designate a function name as global.

Once you use it anywhere in a function, that name is no longer a local name.

Please note that if does not introduce a new scope, only functions and modules (with classes, lists, dict and established understandings are special cases of function areas).

A (hard to read and non-python) job will be to use the globals() function:

 def foo(a): if a: globals()['g'] = 10 else: g = 20