6.2. Functions in Python: Function Definition

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To understand the Python programming language, it is essential to understand the concept of functions. Functions are reusable blocks of code that perform a specific task. They are a great way to organize your code and make it more readable and maintainable. Additionally, functions allow you to reuse the same block of code in multiple parts of your program, saving time and effort.

Definition of Functions

In Python, a function is defined using the 'def' keyword, followed by the function name and parentheses (). Within these parentheses, you can include any parameters the function must accept (if any). You then use a colon (:) to indicate the start of the function's code block. The function body is indented and can contain any amount of code.

def my_function():
    print("Hello world!")

In this example, we define a function called 'my_function' that does not accept any parameters. When we call this function, it will print the string "Hello world!".

Functions with Parameters

Functions can accept any number of parameters. Parameters are variables that are passed to the function when it is called. Within the function, you can use these variables like any other.

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

In this example, the 'greeting' function accepts a parameter called 'name'. When we call this function and pass a string as an argument, it will print a custom greeting.

Functions with Return Values

Functions can also return values. This is done using the 'return' keyword. When a function returns a value, that value can be used elsewhere in your program.

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

In this example, the 'sum' function accepts two parameters and returns their sum. You can use the returned value in other parts of your code, such as in a variable assignment or in an expression.

Functions with Multiple Return Values

Python allows functions to return multiple values ​​at once. This is done by returning the values ​​as a tuple, which is an unchanging, ordered collection of elements.

def min_max(list):
    return min(list), max(list)

In this example, the 'min_max' function returns the minimum and maximum values ​​of a list. When you call this function, you can unpack the returned values ​​into multiple variables.

Functions are an essential part of Python programming and are used in almost all Python programs. They allow you to efficiently organize your code and reuse the same block of code in various parts of your program. With practice, you will become more comfortable with defining and using functions in Python.

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296.3. Functions in Python: Calling Functions