Programming Essentials Python - User Defined Functions - Introduction

User Defined Functions are essential components in programming that allow users to create custom functions for specific tasks within their applications. These functions can be tailored to meet individual needs and streamline the code for efficiency.

Key Concepts Explanation

Defining Functions

Functions in programming are defined using the def keyword followed by the function name and parameters in parentheses. The function block is indicated by indentation.

def my_function(param1, param2):
    # function block
    return result

Doc Strings

Doc Strings are used to provide documentation for functions. They are enclosed in triple quotes and can be accessed using the __doc__ attribute of the function.

def my_function(param1, param2):
    """This is a docstring for my_function."""
    return result

Returning Values

Functions can return values using the return statement. This allows functions to provide output that can be used by other parts of the program.

def add_numbers(num1, num2):
    return num1 + num2

Function Parameters and Arguments

Parameters are placeholders in the function definition, while arguments are the actual values passed to the function when it is called.

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

greet("Alice")  # 'Hello, Alice!'

Varying Arguments

Functions can accept a varying number of arguments using *args for positional arguments and **kwargs for keyword arguments.

def my_function(*args, **kwargs):
    # function block

Keyword Arguments

Keyword arguments allow users to pass arguments to a function by specifying the parameter names, which can enhance readability.

def greet(name, message="Hello"):
    return f"{message}, {name}!"

greet("Bob")  # 'Hello, Bob!'
greet("Alice", message="Hi")  # 'Hi, Alice!'

### Recap of User Defined Functions

User Defined Functions are customizable tools that can be created by users to perform specific tasks within their applications. These functions can streamline code and make it more efficient.

### Passing Functions as Arguments

Functions can also be passed as arguments to other functions, enabling users to create higher-order functions and abstract functionality.

def double(x):
    return x * 2

def apply(func, value):
    return func(value)

apply(double, 5)  # 10

### Lambda Functions

Lambda Functions, also known as anonymous functions, are concise functions that can have any number of arguments but only one expression.

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

### Usage of Lambda Functions

Lambda Functions are useful for creating short, throwaway functions without needing to define a full function. They are commonly used in situations where a function is only needed temporarily.

## Hands-On Tasks

1. Define a function that returns the square of a number.
2. Create a function that accepts a list of numbers and returns the sum of the square of each number.

## Conclusion

User Defined Functions are powerful tools that allow users to customize their code and improve efficiency. By mastering the concepts of defining functions, passing arguments, and utilizing lambda functions, users can enhance their programming skills and create more versatile applications. Practice implementing these concepts in your code and engage with the community to further your learning journey.

[Watch the video tutorial here](