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Tuesday Tip #20: Dictionary comprehensions in Python 📚

Published 8 months ago • 1 min read

Hi Reader,

Tomorrow, I’m re-launching Python Essentials for Data Scientists to celebrate a HUGE course upgrade:

  • NEW: 22 additional video lessons
  • NEW: 7-part project to practice everything you’re learning

There will be a limited-time offer to celebrate the re-launch, so watch out for tomorrow’s email! 💸

I’ll be sending a few extra emails this week. I know your inbox is precious, so I’ll be giving you FREE access to 3 modules from the course! That way, you can benefit regardless of whether you choose to enroll. 💌

Thank YOU for being a valued reader! 🙏 Now let’s get to today’s tip…

👉 Tip #20: Use dictionary comprehensions in Python

Let’s say we had this list of words:

If we wanted to create a list of the word lengths, we could use a for loop:

We start with an empty list, and each time the loop runs, len(word) is appended to the list.

But as you might know, a list comprehension is even better for this scenario:

The effect is the same, but the code is much more concise.

Let’s now pretend that we wanted to create a dictionary containing both the word and its length. Once again, let’s use a for loop:

This time, we start with an empty dictionary, and each time the loop runs, a key-value pair is added to the dictionary.

You can actually convert this into a dictionary comprehension:

The structure is similar to a list comprehension, except there are curly braces { } instead of brackets [ ], and the first part of the comprehension (called the “expression”) is word:len(word) instead of just len(word).

You can read it as follows: “For each word, create a key-value pair of the word and its length.”

Visually, I really like the dictionary comprehension, since the “key:value” structure of the expression matches the way the dictionary prints out!

Let me know if you have any questions! 💬

Today’s tip is just one of the 22 NEW lessons from Python Essentials for Data Scientists!

If you want to build a solid foundation in Python and stay relevant in the world of AI, watch out for tomorrow’s email!

- Kevin

P.S. Weird Al Yankovic is human!

Do you know someone who could benefit from learning Python? Please send them to so that they can hear about the launch! 🚀

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Kevin Markham

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