Functions in Python

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Functions in Python: Reuse Logic, Reduce Mistakes

Functions are the building blocks of any real software. They let you package behavior, name it, and call it again and again.

What this article covers

• defining a function with def
• calling functions
• returning values

Example

def greet(person_name):
    print(f"Hello, {person_name}! Welcome to Python.")

def calculate_total(items, tax_rate):
    subtotal = sum(items)
    return subtotal + subtotal * tax_rate

print(calculate_total([10, 20, 30], 0.18))

Why functions matter

Instead of copying and pasting the same logic, functions let you centralize work. If something changes, you fix it once.

Real-world angle

A function can model a business rule like calculating an invoice total. That same logic can then be used in a web app, script, or automation task.

Next step

Use functions together with collections and modules to build more complex applications.