What are global and nonlocal variables in Python?

Can you explain what global and nonlocal variables are in Python?

Sure! Global variables are defined outside of any function and can be accessed anywhere in the code. Nonlocal variables, on the other hand, are used in nested functions and allow you to assign values to variables in an outer (but not global) scope.

Can you give me an example of how to use a nonlocal variable?

Absolutely! Here's a simple example:

x = 10

def outer_function():
    nonlocal_x = 5
    def inner_function():
        nonlocal nonlocal_x
        nonlocal_x += 1
        print(nonlocal_x)
    inner_function()
    print(nonlocal_x)

outer_function()

This will output 6 and then 6 again, showing how the nonlocal variable is modified.

What happens if I try to modify a global variable inside a function?

If you want to modify a global variable inside a function, you need to use the global keyword. For example:

global_var = 20

def modify_global():
    global global_var
    global_var += 5

modify_global()
print(global_var)  # This will print 25

Are there any best practices for using global and nonlocal variables?

Yes, it's generally best to minimize the use of global variables to avoid unexpected behavior. Use nonlocal variables when you need to modify variables in an outer function scope, but try to keep your functions self-contained when possible.