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How to run a function in Python

Getting Started With Functions in Python

When you're learning to code, the concept of a "function" can seem a little daunting. But don't worry! They're not as complex as they may initially appear. In layman terms, a function is like a mini-program within a program. Imagine a factory where you feed in raw materials (input), and it churns out finished products (output). That's a function!

Now let's dive in and see how we can run a function in Python.

Understanding Functions

A function in Python is defined using the keyword def, followed by the function name and parentheses (). Inside these parentheses, you can include parameters. Parameters are sort of like placeholders for the values that you'll input when you call, or use, the function later. After the parentheses, we use a colon : to signify that we're about to start the function's 'body', i.e., the code that will run when the function is called.

Here's an example of a simple Python function:

def greet():
    print("Hello, world!")

In this example, greet is the function's name, and print("Hello, world!") is the body of the function. This function doesn't take any parameters—it simply prints the phrase "Hello, world!" whenever it's called.

Calling a Function

To "call" a function means to execute the function that you've defined. You can call a function by writing the function's name followed by parentheses. If the function takes any parameters, you'll include them in these parentheses.

Let's call the function we defined earlier:


When you run this code, it will output: Hello, world!.

Using Parameters in a Function

Parameters allow our functions to be more versatile. Let's modify our greet function to take a parameter name.

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

Now, when we call the function, we can pass a name in the parentheses:


This will output: Hello, Alice!.

Returning Values from a Function

We've been using print in our function to see immediate results, but most functions you'll create will use the return statement. return allows a function to produce a value that can be stored in a variable or used in any other manner.

Here's an example:

def square(number):
    return number * number

This function takes a number as a parameter and returns the square of that number. We can store this returned value in a variable like so:

result = square(4)

This will output: 16.


As we've seen, functions are a key part of Python programming. They help keep your code organized, reusable, and easy to read. Just remember the factory analogy we used earlier, and you'll be a function-whizz in no time!

So, the next time you find yourself writing the same chunk of code more than once, consider whether a function might be helpful. And don't forget to experiment, play around with functions, and have fun with it. After all, programming is not just about writing code—it's about solving problems and creating something amazing, one function at a time.

Happy Coding!