What is a defaultdict in Python?

What is a defaultdict in Python?

A defaultdict is a subclass of the built-in dict class in Python. It overrides one method to provide a default value for a nonexistent key.

Can you give me an example of how to use defaultdict?

Sure! Here's a simple example:

from collections import defaultdict

d = defaultdict(int)

d['a'] += 1
print(d)

This will output {'a': 1} because the default value for non-existent keys is 0.

What are some common use cases for defaultdict?

Common use cases include counting items, grouping data, and initializing lists or sets for keys.

Are there any performance benefits to using defaultdict?

Yes, defaultdict can improve performance by eliminating the need to check for key existence before accessing or modifying values.