Bite-Size Python

11Functions

Programs in Python often repeat the same set of actions defined in a block of code. Rather than rewrite the same block of code repeatedly in your program, create a function that you can use anywhere you need.

Create a Function

In Python, every function has a name, which is what you use to call it. Here's the syntax for defining a function:

All functions start with the keyword def followed by the name of the function and a pair of parentheses. Just below the function is the function body. The function body contains whatever actions you choose to have your function complete.

Here is an example of a hello_world function that prints the string "Hello World":

>>> def hello_world():
        print("Hello World") 

Call a Function

The function in the prior example won't do anything in your program until you call the function. Calling a function tells your code to run the code inside the function body. To call a function, use the function name and include the parentheses. The parentheses specifically say, “Treat the name as a function and call it.”

>>> hello_world()
Hello World
 

Notice how you don't need to include a print statement in the function call. Since the hello_world() function includes a print statement in the function body, the string inside the function prints whenever the function is called.

It's worth noting that a function can do more than print strings! Essentially, ...