Lesson 4: Functions in Python

 In this lesson, we will learn about functions in Python and how to use them to organize and reuse code.

A function is a block of code that can be called by a name and that can accept arguments (inputs) and return a value (output).

Here is an example of how to define a function in Python:

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

This function, called greet, takes one argument (a string called name) and prints a greeting message to the console.

To call a function, you simply need to use its name followed by parentheses and any necessary arguments.

Here is an example of how to call the greet function:

greet('John')  # prints 'Hello, John!'

You can also define a function that returns a value using the return statement.

Here is an example of a function that returns a value:

def square(x):
    return x ** 2

This function, called square, takes one argument (a number called x) and returns the square of thatnumber.

To use the returned value of a function, you can assign it to a variable or use it in an expression.

Here is an example of how to use the returned value of a function:

result = square(3)  # result is now 9
print(square(4) + 2)  # prints 18

You can also specify default values for function arguments. This allows you to call the function without specifying a value for that argument, in which case the default value will be used.

Here is an example of how to specify default values for function arguments:

def greet(name='John'):
    print('Hello, ' + name + '!')

greet()  # prints 'Hello, John!'
greet('Jane')  # prints 'Hello, Jane!'

In this example, the greet function has a default value of 'John' for the name argument. If no value is specified when calling the function, the default value is used. If a value is specified, it overrides the default value.

Functions can also accept an arbitrary number of arguments using the *args notation. This allows you to pass a variable number of arguments to the function.

Here is an example of how to use the *args notation:

def sum(*numbers):
    total = 0
    for number in numbers:
        total += number
    return total

print(sum(1, 2, 3))  # prints 6
print(sum(1, 2, 3, 4, 5))  # prints 15

In this example, the sum function takes an arbitrary number of arguments (stored in a tuple called numbers) and returns the sum of those numbers.

Conclusion

That's it for this Python tutorial series! We have covered the basics of the Python programming language, including data types, control structures, and functions.

There is still much more to learn about Python, including modules and packages, object-oriented programming, and advanced data structures and algorithms. I encourage you to continue learning and exploring the possibilities of Python.

I hope you found this tutorial series helpful and that you are now comfortable with the basics of Python. Happy coding!