Functions

In the world of design, planning and repetition are key. We often find ourselves repeating similar tasks. In Python, we can simplify these repetitive tasks using something called a function.

What is a Function?

Think of a function as a blueprint for a timber structure. This blueprint is a set of instructions that tells us how to build a particular structure. Similarly, a function in Python is a set of instructions that performs a specific task. Just like how we can use the same blueprint to build multiple structures, we can use the same function to perform the same task multiple times.

Creating a Function

Let’s consider a simple task: calculating the volume of a timber beam. In Python, we can create a function to do this for us.

def calculate_beam_volume(length, width, height):
  volume = length * width * height
  return volume

In this example:

def is a keyword that tells Python we are creating a function.
calculate_beam_volume is the name of our function. In Python, we should always use snake case to name functions, e.g. this_is_my_function_name().
(length, width, height) are the parameters of our function. These are the names of the variables we will feed into our function.
: indicates the start of the function’s implementation.
return is a keyword that returns a value out of the function. A function can work also without it.
an indent: beware that all the function’s body has to be indented. Otherwise your python interpreter will throw an error.
length * width * height is the calculation that our function will perform.
volume is the variable that will store the result of our calculation.
volume is the value that our function will return.

Calling a Function

Now that we have created our function, we can call it to perform the calculation. To do this, we simply write the name of the function followed by the values we want to feed into it.

calculate_beam_volume(10, 20, 30)

The return value can be stored in a variable.

beam_volume = calculate_beam_volume(10, 20, 30)
print(beam_volume)

This will output the 1.0, the volume of the beam.

Why Do We Need Functions?

Functions in Python, like blueprints in architecture, allow us to simplify complex tasks and repeat them easily and accurately. They are a powerful tool in any Python programmer’s toolkit:

(i) ♻️ Functions are a good tool to avoid repetitions: functions are a nice tool to store a code that you would need to use multiple times. This is fundamental since every time your rewrite the same code, you double the chances of creating a bug or an error. If well thought and written, functions can avoid that. Consider the following scenario:

As you can see we can actually call the same function twice but with different parameters.

(ii) 📦 Functions allow to organize your code: Consider the following code:

# my script
## A) my first part of code: it does something and produce result a
  ### line of code 1
  ### line of code 2
  ### line of code 3
  ### ...
## B) my second part of code: it does something and produce result b
  ### line of code 16
  ### line of code 17
  ### line of code 18
  ### ...
## C) my second part of code: it does something and produce result c
  ### line of code 36
  ### line of code 37
  ### line of code 38
  ### ...

By using functions it can be reworked to be much more organized and readable like so:

def func_a():
  ### line of code 1
  ### line of code 2
  ### line of code 3
  ### ...

def func_b():
  ### line of code 16
  ### line of code 17
  ### line of code 18
  ### ...

def func_c():
  ### line of code 36
  ### line of code 37
  ### line of code 38
  ### ...

def func_abc():
  func_a()
  func_b()
  func_c()

func_abc()  # <-- this is the called function

🛠 Exercises

01: 🐍⬇️⬇️⬇️ Download the script here ⬇️⬇️⬇️🐍 02: 🐍⬇️⬇️⬇️ Download the script here ⬇️⬇️⬇️🐍 03: 🐍⬇️⬇️⬇️ Download the script here ⬇️⬇️⬇️🐍

Solutions: