Python Function Tutorial
Published: 2023-02-21 15:42:06



Python function is a block of reusable code that performs a specific task. Functions can be called multiple times from within a program, which allows for efficient code reuse and organization. In Python, functions are defined using the "def" keyword, followed by the function name, a set of parentheses, and a colon. The body of the function is indented below the function definition.

Functions can take parameters, which are passed to the function when it is called. Functions can also return values, which can be used by the calling code. Python functions can have default parameter values, making them more flexible and easier to use.

Functions are an essential part of Python programming and are used extensively in all types of applications. They allow developers to organize their code and improve its readability, maintainability, and reusability.

## [**Python Function Example**](https://www.programdoc.com/python/functions)

```py
def greet(name):
    # This function greets the person passed in as a parameter
    print("Hello, " + name + ". How are you today?")

greet("Max")
``` 

Output:
`Hello, Max. How are you today?` 

In the above example, we have defined a function named `greet` which takes one parameter `name`. The function prints a greeting message to the console, using the `print()` statement.

To call the function, we simply pass the name of the person we want to greet as an argument to the `greet()` function.

## Python Function with Return Type Example

```py
def add_numbers(x, y):
    # This function takes two numbers as input and returns their sum
    return x + y

result = add_numbers(5, 10)
print("The sum of 5 and 10 is:", result)
``` 

Output:
`The sum of 5 and 10 is: 15` 

In this example, we have defined a function named `add_numbers` which takes two parameters `x` and `y`. The function returns the sum of `x` and `y` using the `return` statement.

We call the `add_numbers()` function and store its result in a variable named `result`. We then print the result to the console using the `print()` statement.

## Python Function with Default Arguments Example

```py
def print_message(name, message="Hello"):
    # This function prints a message to the console
    print(message + ", " + name + "!")

print_message("Max")
print_message("Bob", "Good morning")
``` 

Output:
```py
Hello, Max!
Good morning, Bob!
``` 

In this example, we have defined a function named `print_message` which takes two parameters: `name` and `message`. The `message` parameter has a default value of `"Hello"`.

If we call the function with only one argument (`name`), it will use the default value for `message`. If we call the function with two arguments (`name` and `message`), it will use the value we passed in for `message`.

## Assigning a Function to a Variable Example

```py
def print_hello():
    print("Hello, world!")

greeting = print_hello
greeting()
``` 

Output:
`Hello, world!` 

In this example, we have defined a function named `say_hello` which prints a greeting message to the console. We then assign the `say_hello()` function to a variable named `greeting`.

We can call the `greeting()` function to execute the `say_hello()` function and print the greeting message to the console.




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