How Do Python Functions Modify Global Variables?

Global Variables in Python Functions

When using global variables in Python, it's crucial to understand the appropriate way to modify their values. While it's generally recommended to avoid global variables due to their potential for confusion, let's examine a scenario where their use may be necessary.

If the goal is to access a global variable, simply use its name within the function. However, to modify a global variable and make the change permanent, you must employ the global keyword.

For instance:

global someVar
someVar = 55

This line will set the global variable someVar to 55. If the global keyword is omitted, Python will create a local variable named someVar and assign it the value of 55, leaving the global variable untouched.

With regard to the functions mentioned in the query:

x = "somevalue"

def func_A():
    global x
    # Do things to x
    return x

def func_B():
    x = func_A()
    # Do things
    return x

func_A()
func_B()

When calling func_A, it will modify the global variable x. Then, when func_B is called, it will reassign the local variable x to the value returned by func_A, which is the modified global variable. Consequently, func_B will operate on the same global variable that func_A modified.

It's important to note that the order of function definitions does not affect the behavior, but the order of function calls does. Calling func_A before func_B ensures that the global variable is modified before func_B accesses it.

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