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Watch Me Code - Solving Bite 21. Query a Nested Data Structure

Posted by Bob on Sat 14 July 2018 in CodeChalleng.es • 2 min read

I recorded a video solving Bite 21. Query a nested data structure. The exercise presents us with a dictionary of car manufacturers and their corresponding car models. We will extract various bits and pieces from it as well as sort the nested model lists. This is a common type of data structure so specially for a beginner it is important to have this become second nature. Prepare to learn more about looping, some string operations, and list / dict comprehensions.


Before watching the solution video, we highly encourage you to follow this promo link and try it yourself. Seriously, you learn n times more by having tried it yourself and comparing your solution to ours or via the Bite Forum feature (see at the end of the video). Enjoy!

Ready for the solution?


  • When you don't need (key, value) pairs, instead of items you can use keys() or values().

  • join is a super handy string method to know about: return ', '.join(cars['Jeep'])

  • List comprehensions are one of our favorite features, I write them from the inside out and would probably not use more than one for loop: return [models[0] for models in cars.values()]

  • You can flatten a list of lists like this: models = sum(cars.values(), [])

  • You can use a dictionary comprehension to modify an existing dict and returning a new dict, all in one go:

    return {manufacturer: sorted(models) for
            manufacturer, models in cars.items()}

    It doesn't really matter here but just to note: sorted returns a new list object, while list.sort() would sort in-place.

  • We defined this Bite some time ago, and I forgot about some parts of the solution. This served two purposes:

    • Making mistakes and/or not coming to the best solution at first is actually a good thing. This is part of the learning: going through the struggle and contrasting an earlier iteration with a later one.
    • It is good to know that once solved you can go back after some time and use a Bite to refresh your knowledge!
  • As you saw towards the end we have a forum for each Bite now where you can share / discuss your solution with other community members. This will only add to the learning. Note this is only accessible if you have resolved the Bite to avoid any spoilers.


If you are stuck and don't want to use the solution button - after all this would deduct points (unless it's an Intro Bite) - you can ask for help using our #codechallenges Slack channel. To join our Slack confirm your email on our platform, then opt-in to Slack under Settings.

What did you learn?

Where there other insights you got while doing this Bite exercise? We hope to salute you on the platform and Slack. And remember ...

Keep Calm and Code in Python!

-- Bob

See an error in this post? Please submit a pull request on Github.