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 provides a default value for the key that does not exist. This is particularly useful in scenarios like counting occurrences, grouping items, or initializing lists.

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

Sure! Here's a simple example:

from collections import defaultdict

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

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

print(item_count)

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

What about using defaultdict for grouping items?

You can use defaultdict with lists to group items. For example:

from collections import defaultdict

grouped_items = defaultdict(list)
items = [('fruit', 'apple'), ('fruit', 'banana'), ('vegetable', 'carrot')]

for category, item in items:
    grouped_items[category].append(item)

print(grouped_items)

This will output: defaultdict(<class 'list'>, {'fruit': ['apple', 'banana'], 'vegetable': ['carrot']}).