Variable Scope and Nested Functions

In Python, where a variable is defined determines where it can be accessed — this is called scope.
Functions can also be nested, meaning one function can exist inside another.

Let’s explore both.

Variables defined inside a function are local — they only exist while the function runs.
Variables defined outside any function are global and can be used throughout the script.

복사
message = "Hello from global scope"

def show_message():
    message = "Hello from local scope"
    print(message)

show_message()
print(message)

Explanation:

• Inside the function, a new message variable is created.
• The global variable is unaffected.

To modify a global variable inside a function, use the global keyword.

복사
counter = 0

def increase():
    global counter
    counter += 1

increase()
print("Counter:", counter)

Explanation:

• Without global, Python treats counter as a new local variable.
• With global, it updates the variable outside the function.

A function can be defined inside another function. The inner function is local to the outer one.

복사
def outer():
    print("Outer function")

    def inner():
        print("Inner function")

    inner()

outer()

Explanation:

• inner() can only be called inside outer().
• Useful for organizing logic and encapsulating behavior.

Next, you’ll learn how to handle errors gracefully using try, except, and related tools.