Lesson start ideas	Give a creative idea how to begin a lesson
Which subject	Computer science
What age group	College
What topic	User defined functions in python
Quantity	1
Any other preferences

Welcome to the exciting world of computer science! In this lesson, we will be exploring user-defined functions in the Python programming language. A user-defined function is a set of instructions that can be reused multiple times in a program. This allows for more efficient and concise coding.

What is a Function?

Before we dive into user-defined functions, let's refresh our memory on what a function is in programming. A function is a block of code that performs a specific task. It can take in input values and produce output values. Functions are a fundamental concept in programming, as they allow us to organize code into modular blocks that can be easily reused.

User-Defined Functions

Now that we know what a function is, let's explore how we can create our own functions in Python. User-defined functions are created by the programmer and are tailored to their specific needs. To create a function, we use the def keyword followed by the name of the function and its parameters. Here is an example:

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

In the example above, we have defined a function called greet that takes in a parameter name. This function simply prints out a greeting to the screen with the name of the person we pass in as an argument.

Calling a Function

Now that we have created our function, we can call it by passing in an argument for the name parameter. Here's an example:

greet("John")

This will output the following to the screen:

Hello, John!

Conclusion

Congratulations! You now have a basic understanding of user-defined functions in Python. These functions are a powerful tool that can help you write more efficient and modular code. Be sure to practice creating your own functions and experimenting with different parameters and return values. Happy coding!