scope.md

Variable scope

Python distinguishes local and global variable scope:

local scope refers to variables that only exist within a function.

global scope refers to variables that are taken from the next level above the function definition. Usually this is the module (unless you have nested functions).

Knowing when a variable is local and when global is especially important when writing values. To avoid trouble, it is a good idea to avoid global variable most of the time. Still you need to know the difference

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Exercise

Guess the value of the variable 'a' in the three programs. Check your guess by running the code.

Example 1:

:::python
def addition(number1, number2):
    """Just adds two numbers."""
    a = number1 + number2
    return a

a = 3
b = 5
c = addition(a, b)
print(a)

Example 2:

:::python
def addition(number1, number2):
    """Just adds two numbers."""
    global a
    a = number1 + number2
    return a

a = 3
b = 5
c = addition(a, b)
print(a)

Example 3:

:::python
def addition(number1, number2):
    """Just adds two numbers."""
    a = number1 + number2
    global a
    return a

a = 3
b = 5
c = addition(a, b)
print(a)