What is the difference between defaultdict and dictionary in Python?

What is the difference between defaultdict and dictionary in Python?

In Python, a dictionary is a built-in data type that stores key-value pairs. A defaultdict, from the collections module, is a subclass of the dictionary that provides 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

# Create a defaultdict with a default value of 0
my_dict = defaultdict(int)

# Accessing a nonexistent key returns the default value
print(my_dict['missing_key'])  # Output: 0

# Adding values
my_dict['key1'] += 1
print(my_dict['key1'])  # Output: 1

When should I use defaultdict instead of a regular dictionary?

You should use defaultdict when you want to avoid key errors and provide a default value for missing keys, which can simplify your code.

Are there any performance differences between the two?

Generally, defaultdict can be slightly slower than a regular dictionary due to the overhead of handling default values, but the difference is often negligible.