What Are Comprehensions?

Comprehensions let you write shorter, cleaner, and faster code.

Whether you're dealing with lists, dictionaries, sets, or even variables - comprehensions will save you a lot time and effort.

Plus, they make for some pretty impressive one-liners!

If Comprehensions

Let's begin with simple if/else Statement comprehensions.

They let you combine simple logical statements into a single line. They are great to use when you need to check something and assign one of 2 available values.

I'm going to provide you 2 code examples with the same result, and I want you to tell me which one is easier to read.

Example #1:

Example #2:

I hope we can agree that Example #2 is more pythonic 🐍.

Also, it's very self-explanatory. You can literally read it as English and it makes sense.

Simple List Comprehensions

Now it's time to focus on the most used comprehensions in python - List Comprehensions.

They are a great way to transform, filter or create new lists in a more pythonic way. They allow you to create a loop and generate a new list of data from a single line of code.

Here is the List Comprehension Anatomy:

As you can see you can put your for-loop inside of square brackets, and the first expression is what will be added to the new list.

Let's have a look at 2 code examples again, and you tell me which one you prefer more.

Both examples will take items from an existing list and create a new list with UPPERCASE items (The same principle can be applied for anything else.)

Example #1:

Example #2:

Would you rather write Example #1 or Example #2?​
👉I bet it's #2!

List Comprehensions with Logic

I hope you already see how powerful comprehensions can be in your scripts.

However, some of you probably start wondering: 'But what if you want to add logic with if-statements'? Well, that's also possible.

Here is an extended anatomy of list comprehensions:

As you can see, we can create a for-loop in the middle, then specify expression of what will be returned on the left, and then conditions on the right.

This way you will only get items in your new list if they pass the condition. Otherwise they will be ignored. This is a huge time saver to filter your lists.

I will use the same example and add a simple filtering to ensure it contains 'item_' keyword.

P.S.

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