Functions

A function is a block of organized, reusable code that is used to perform a single, related action. Functions provide better modularity for your application and a high degree of code reusing.

In Python, we use the def keyword to define a function.

1. The Structure of a Function

• Definition: Starts with def, followed by the function name and parentheses ().

• Parameters: Inputs to the function placed inside the parentheses.

• Body: The indented code that executes when the function is called.

• Return: The return statement sends a result back to the caller. If no return is specified, the function returns None.

2. Arguments: Positional, Keyword, and Default

Python offers great flexibility in how you pass data to functions:

• Positional: Arguments passed in the correct order.

• Default: You can assign a value to a parameter in the definition so it's optional during the call.

• Keyword: You can pass arguments by name, so the order doesn't matter.

# Function with a default parameter
def greet(name, message="Welcome to the team!"):
    return f"Hello {name}, {message}"

# 1. Calling with both arguments (Positional)
print(greet("Alice", "Good Morning!"))

# 2. Calling with only the required argument (Using Default)
print(greet("Bob"))

# 3. Calling with Keyword arguments (Order changed)
print(greet(message="How are you?", name="Charlie"))

# Function to calculate area
def calculate_area(length, width):
    area = length * width
    return area

result = calculate_area(5, 10)
print(f"Area: {result}")

3. Scope of Variables

• Local Scope: Variables created inside a function belong to that function and cannot be accessed outside.

• Global Scope: Variables created in the main body of the script are accessible everywhere.