When should I use defaultdict instead of a regular dict?

When should I use defaultdict instead of a regular dict?

You should use defaultdict when you want to provide a default value for a nonexistent key, which simplifies your code.

Can you give me an example of how defaultdict works?

Sure! For instance, if you want to count occurrences of items, you can use defaultdict(int) to initialize counts to 0 automatically.

What happens if I try to access a key that doesn't exist in a regular dict?

In a regular dict, accessing a nonexistent key raises a KeyError, while defaultdict returns the default value you specified.

Are there any downsides to using defaultdict?

One downside is that it can hide bugs if you're not careful, as it creates keys automatically without explicit checks.