When it comes to Python, the key word for defining functions is def. By using the def keyword, we can create custom functions to perform specific tasks. A function is a reusable piece of code that can take input parameters and return results. Let's dive into a detailed tutorial on how to define functions in Python.

How to Define Functions in Python

The basic syntax for defining functions in Python is as follows:

def function_name(parameter1, parameter2, ...):
    function_body
    return return_value

def is the keyword for defining a function, function_name is the name you give to your function, parameter1, parameter2, ... are the input parameters the function takes, function_body is the code block that performs the specific task, and return keyword is used to return the result of the function.

A Simple Function Example

Here is a simple example of a function that takes two parameters and returns their sum:

def add(a, b):
    result = a + b
    return result

# Call the function
sum_result = add(3, 5)
print("The sum of the two numbers is:", sum_result)

In this example, we defined a function named add that takes two parameters a and b. The code in the function body calculates the sum of these two parameters and stores the result in the variable result. We use the return keyword to return the calculated result.

Setting Default Values for Function Parameters

Python allows you to set default values for function parameters. When calling a function, if a corresponding parameter value is not provided, the default value will be used. This can be achieved by assigning values to parameters in the function definition.

def greet(name, message="Hello"):
    print(message, name)

# Call the function
greet("John")  # Output: Hello John
greet("Jane", "Welcome")  # Output: Welcome Jane

In this example, we set the default value "Hello" for the message parameter of the greet function. When we call the function without providing a value for the message parameter, the default value is used.

Returning Values from Functions

A function can use the return keyword to return a value. The return value can be any valid Python expression, such as numbers, strings, lists, etc.

def square(x):
    return x * x

# Call the function
result = square(5)
print("The square of 5 is:", result)  # Output: The square of 5 is: 25

In this example, we defined a function named square that takes a parameter x. The code in the function body calculates the square of x and returns the result using the return keyword.

In Python, we use the def keyword to define functions. Functions can take input parameters and return results. Default values can be set for function parameters to omit certain parameters when calling the function. The return keyword is used to return the result of the function. By defining functions, we can write more modular and reusable code, improving programming efficiency.

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