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Features in Python are Like a Espresso Machine

Features in Python are one among these subjects for inexperienced persons! Most perceive what features are at a primary stage. Nonetheless, there’s rather more element and nuance to defining and calling features in Python.

As with most issues in coding and Python, there’s nothing higher than a very good analogy to image what’s occurring behind the scenes.

On this article, you’ll learn how features in Python are like espresso machines. You’ll examine:

  • parameters and arguments
  • defining and calling features
  • shifting knowledge out of a operate utilizing a return assertion

Time to make your self a cup of espresso, sit down (or stand if, like me, you employ a standing desk), and luxuriate in each the espresso and the article.

What Does A Espresso Machine Want?

There are numerous various kinds of espresso machines, in fact. I’ll use the one I’ve on my kitchen bench for instance. Right here it’s:

Coffee machine making coffee

However the analogy works for different kinds of espresso machines, too!

The espresso machine’s instruction guide will let you know the belongings you’ll want earlier than you can also make your espresso:

  • water
  • electrical energy
  • floor espresso or espresso pods

Let’s have a look at a pseudo-function signature—the road you’d write when defining a “espresso machine” operate:

def make_coffee(water, electrical energy, espresso):

The operate definition has three parameters. Because of this for this operate to work, it should want one thing to fill these three placeholders.

Defining the operate shouldn’t be sufficient. Entry to a operate definition, whether or not you write your personal or import from a module, is the equal of shopping for the espresso machine, unpacking it, and discovering a spot to place it in your kitchen.

It is advisable to flip it on…

Turning On The Espresso Machine — Calling A Perform in Python

Earlier than you activate the espresso machine, you need to put within the substances. The machine has a spot prepared for these. These placeholders are:

  • the tank the place the water will go
  • the plug to provide electrical energy
  • the holder for the espresso pod

These are the parameters. They’re the placeholders which had been current since you obtain the machine—or outlined the operate.

Now it’s essential to put the issues wanted within the machine.

You might use faucet water, or filtered water, or bottled water (actually?!) within the water tank. And if you happen to use espresso pods, you’ll have a range to select from.

No matter you select would be the argument whenever you name the operate.

Right here’s what a operate name may appear like:


Calling the operate is the equal of turning the machine on and urgent the button to make the espresso.

The brackets you employ whenever you name a operate are the “on” button of a operate in Python. The truth is, there’s a resemblance between the standard “on” button on most units and the brackets or parentheses ( ):

Do You Know How The Espresso Machine Works?

When you simply need to use the espresso machine to make espresso, you don’t must understand how the espresso machine works on the within. Does it have motors? What concerning the electronics? You don’t actually care so long as you may put the water within the tank, put the espresso pod in its holder, plug within the machine and switch it on.

If you use a operate, whether or not it’s one that you simply or another person wrote, you don’t must know what’s contained in the operate definition.

So long as you know the way to make use of the operate, you don’t must know what code is written inside. It is advisable to know what arguments are wanted and what the operate returns, however not how the operate performs the actions it does.

Within the espresso machine analogy, the instruction guide doesn’t let you know how the machine works on the within. It simply tells you the way to use it.

Nonetheless, if you happen to’re an engineer constructing a espresso machine, otherwise you’re tempted to open your espresso machine to repair it or (maybe) enhance it, then it’s essential to know the way it works. It is advisable to know the code contained in the operate definition—particularly if you happen to’re the one writing it!

Making The Espresso and Making Positive You Don’t Waste It!

So, you’ve put within the water and the espresso pods and plugged the machine into the wall socket.

You flip it on.

You hear a whizzing sound, and a brief second later, the espresso begins pouring out of the nozzle on the prime of the machine…

And the espresso pours straight into the drainage tray on the backside, ultimately overflowing and making a multitude in your kitchen bench.


We’ll return to this downside shortly.

What Does The Machine Return?

Features return knowledge. Even these features in Python that “don’t return something” return the item None. A Python operate can not return nothing. As a substitute, it returns None when there’s nothing else to return.

Nonetheless, many features do return some knowledge. Let’s have a look at this instance:

import random

def do_something(first, second):
    end result = first + second + random.randint(-5, 5)
    return end result

The eagle-eyed reader might discover that the variable end result shouldn’t be wanted on this operate, however I’ve included it for the needs of the dialogue coming subsequent.

What does this operate return? Right here’s the pedantic reply, however the pedantry is necessary on this case.

The operate does not return end result. It doesn’t return a variable named end result. It returns the contents of the native variable end result.

If a variable is a field containing the information and the variable title is the label on the surface of the field, a operate doesn’t return the field nevertheless it ideas it over and returns its contents.

For this reason the next code returns a NameError:

import random

def do_something(first, second):
    end result = first + second + random.randint(-5, 5)
    return end result

do_something(3, 5)
print(end result)

The error says that title 'end result' shouldn't be outlined. In the primary scope of this program, the title end result has by no means been created. It solely exists as an area variable throughout the confines of the operate do_something().

So what’s occurred to the espresso? You turned the espresso machine on with a name that might have appeared like this:


The operate returns the liquid espresso, which pours out of the machine’s nozzle. However you didn’t create a variable to gather the espresso returned by the operate. You’re not storing the information that’s returned. Identical to the espresso, the information returned by a operate can be misplaced if you happen to don’t use it instantly or retailer it someplace.

You may strive the next:

coffee_cup = make_coffee(

Now, you’re gathering the espresso returned in a variable named coffee_cup.

A transparent coffee cup with coffee using in the Coffee Machine Functions in Python analogy

Time to make one other espresso?

Closing Phrases

The espresso machine analogy is one among my favourites in programming. Like all analogies, it’s not excellent, and there’s a restrict on how far you may take it. You most likely must “surrender espresso” whenever you transfer to default arguments or *args and **kwargs, say.

Nonetheless, it offers a very good image of the excellence between defining and calling a operate in Python, and between parameters and arguments. It additionally supplies a very good visualisation of what occurs when a operate returns knowledge and the way it’s essential to accumulate these knowledge in a variable whenever you name the operate.

Additional Studying

  • When you like analogies, right here’s one other perspective of features in Python via The Perform Room analogy, a part of The White Room analogy.
  • And you too can learn the complete White Room analogy which accounts for extra components of a pc program.

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