Types of Functions

Here’s a clear and friendly guide to the types of functions in Python, with examples, emojis, and practice questions! 🚀

1. Built-in Functions 🏗️

These are functions that Python provides by default—no need to define them yourself!

Examples:

print("Hello!")      # Prints to the screen
len([1, 2, 3])       # Returns length of a list
max(4, 7, 2)         # Returns the largest value

2. User-defined Functions ✍️

These are functions you create using the def keyword.

Example:

def greet(name):
    print(f"Hello, {name}!")

greet("Alice")  # Output: Hello, Alice!

3. Fruitful Functions (Return a Value) 🍎

These functions return a value using the return statement.

Example:

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

result = add(2, 3)
print(result)  # Output: 5

• Also called non-void functions¹.

4. Void Functions (No Return Value) 🚫

These functions do not return a value. They might print something or perform an action.

Example:

def print_hello():
    print("Hello!")

x = print_hello()  # Output: Hello!
print(x)           # Output: None

• The special value None is returned automatically¹.

5. Anonymous (Lambda) Functions ⚡

Quick, unnamed functions defined with the lambda keyword.

Example:

double = lambda x: x * 2
print(double(5))  # Output: 10

6. Recursive Functions 🔁

Functions that call themselves to solve a problem.

Example:

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

print(factorial(5))  # Output: 120

7. Module Functions 📦

Functions defined inside a module (a separate Python file) and imported for use.

Example:

import math
print(math.sqrt(16))  # Output: 4.0

• sqrt() is a function in the math module².

8. Methods 🛠️

Functions that belong to objects (like lists, strings, etc.).

Example:

my_list = [1, 2, 3]
my_list.append(4)  # append() is a list method

• Methods are called with a dot, like object.method()³.

Practice Questions & Solutions 📝

1️⃣ Write a fruitful function that returns the square of a number.

def square(x):
    return x * x

print(square(6))  # Output: 36

2️⃣ Write a void function that prints “Good morning!”.

def say_morning():
    print("Good morning!")

say_morning()  # Output: Good morning!

3️⃣ Use a lambda function to triple a number.

triple = lambda x: x * 3
print(triple(4))  # Output: 12

4️⃣ What type of function is math.sin()? How do you use it?

import math
print(math.sin(0))  # Output: 0.0

5️⃣ Write a recursive function to sum all numbers from 1 to n.

def sum_to_n(n):
    if n == 1:
        return 1
    else:
        return n + sum_to_n(n-1)

print(sum_to_n(5))  # Output: 15

Key Points with Emojis 🎯

• Built-in: Provided by Python 🏗️
• User-defined: You create them ✍️
• Fruitful: Return a value 🍎
• Void: No return 🚫
• Lambda: Anonymous, quick ⚡
• Recursive: Call themselves 🔁
• Module: From imported files 📦
• Methods: Belong to objects 🛠️

If you want more details or examples for any type, just ask! 😃

References:

• Fruitful (returning value) and void (no return) functions are common distinctions in Python¹.
• Module functions are imported from modules like math².
• Methods are functions bound to objects, such as strings and lists³.