Understanding defaultdict() in Python

Introduction:

Recently I’ve been solving some Leetcode problems and I’ve came across something new: The ‘defaultdict’.

I’m not entirely familiar with it so I’m using this week’s blog post as an opportunity to document my experiences with it (As well as stumbling across it) as well as highlight the key distinctions between a standard dictionary and a defaultdict in Python.

As always, before we get into the content, please make sure to applaud, comment and share with your friends.

Happy Reading!

So What is a Standard Dictionary in Python?

Python Dictionary — Key value store in Python.

If we try to access a value in the dictionary that doesn’t exist then this results in an error.

Introducing the defaultdict():

This is where the defaultdict() shines as its whole purpose it to avoid this KeyError.

By assigning a default value, this prevents an error from being raised.

You can even pass in a default value data type (for e.g. list or int).

Note that defaultdict is imported from Collections.

Use Cases of defaultdict:

As stated earlier, the main use case here is to avoid KeyError’s as well as mapping one value to another.

One recent example for me was completing “Find Players With One or Zero Losses” LeetCode problem as I had to map players to their number of wins and losses.

Conclusion:

Like I said earlier, I wasn’t really aware of defaultdict() earlier and this blog post just aims to consolidate knowledge and document an anecdote.

I hope that this blog post simplifies the concepts and summarises the differences between a dictionary and defaultdict.

Final Things:

As always, thank you for taking the time to read this article!

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