Comprehensive Guide to Functions in Python: Structure, Types, and Use Cases

1. Defining a Function

Functions are defined using the def keyword:

def greet(name):
    print("Hello", name)

2. Calling a Function

greet("Jina")
# Output: Hello Jina

3. Return Values

def add(a, b):
    return a + b

result = add(5, 3)
# Output: 8

4. Types of Arguments

• Positional arguments: Based on order
• Keyword arguments: Specified by name
• Default values: def show(name="guest")
• *args and **kwargs: Handle variable-length arguments

5. Built-in Functions

Python provides functions like len(), type(), and print() out of the box.

6. Recursive Functions

A function calling itself:

def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n-1)

7. Lambda Functions

Anonymous functions for quick computations:

square = lambda x: x ** 2
print(square(4))  # Output: 16

8. Variable Scope

• Global: Accessible throughout the program
• Local: Confined to the function in which it’s defined

9. Function Documentation (Docstring)

def greet(name):
    """Displays a welcome message"""
    print("Hello", name)

10. Conclusion

Functions are central to writing clean and scalable Python code. Learning to define them, manage arguments, and apply advanced concepts like recursion or lambda expressions is key to mastering the language.