Clarity on global variables

[DeaD_EyE]

The global is only required if you do an assignment.

Assign the int 42 to the name a

a = 42

An assignment inside a function is in function scope and does not affect module scope.

a = 42


def foo():
    a = 13
    print(a)


foo()      # prints 13
print(a)  # prints 42

Now the same with global:

a = 42


def foo():
    global a
    # a is now assigned on module scope
    a = 13
    print(a)


foo()      # prints 13
print(a)  # prints 13

If you have mutable objects, then you don't need global.

my_list = [1, 2, 3]


def sideeffect():
    # here is no assignment
    # instead the mutable object is modified inline
    my_list.append(10)


print(my_list) # [1, 2, 3]
sideeffect()
print(my_list) # [1, 2, 3, 10]

You can mutate mutable objects on module scope from a function without the use of global.
I named the function sideeffect because the function is causing a side effect. my_list is modified on module scope.

The best way to get rid of global are classes. A class holds state and has methods, which are doing something with the state. The instances of classes are isolated from each other.

class MyList:
    """
    Usually a class has more than one method.
    This is a very minimal example.
    """
    def __init__(self, elements=None):
        # self is the instance of the class and elements holds the list, which
        # was created during instantiation (__init__) 
        self.elements = elements or []  # if elements is None, then [] is assigned to self.elements

    def add(self):
        self.elements.append(10)

l1 = MyList()
l2 = MyList()

l1.add()
l1.add()
l2.add()

print(l1.elements) # [10, 10]
print(l2.elements) # [10]

You should read this article: https://realpython.com/python-scope-legb...-namespace
It explains the different namespaces and some Python internals.