class Foo:
my_global = None
def __init__(self):
pass
@classmethod
def change_my_global(cls):
cls.my_global = 10
a = Foo()
b = Foo()
print(a.my_global)
print(Foo.my_global)
print(b.my_global)
a.change_my_global()
print(a.my_global)
print(Foo.my_global)
print(b.my_global)
