What are some use cases for defaultdict in Python?

What are some use cases for defaultdict in Python?

The defaultdict is a subclass of the built-in dict class. It overrides one method to provide a default value for a nonexistent key. This can be particularly useful in various scenarios. For example, you can use it to count occurrences of items in a list.

Can you give me an example of counting items using defaultdict?

Sure! Here's a simple example:

from collections import defaultdict

item_counts = defaultdict(int)
items = ['apple', 'banana', 'apple', 'orange', 'banana', 'banana']

for item in items:
    item_counts[item] += 1

print(item_counts)

This will output: defaultdict(<class 'int'>, {'apple': 2, 'banana': 3, 'orange': 1}).

What other scenarios can defaultdict be useful in?

It can be useful for grouping items, creating adjacency lists for graphs, or even for initializing complex data structures without having to check if keys exist.

Are there any performance benefits to using defaultdict?

Yes, using defaultdict can improve performance by reducing the number of key existence checks, which can be beneficial in large datasets.