How do I initialize a defaultdict in Python?

How do I initialize a defaultdict in Python?

You can initialize a defaultdict by importing it from the collections module and specifying a default factory. For example: from collections import defaultdict and then my_dict = defaultdict(int).

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

If you access a key that doesn't exist, it will return the default value specified by the factory. For example, if you used int, it will return 0.

Can I use a custom function as the default factory?

Yes, you can use any callable as the default factory. For instance, my_dict = defaultdict(lambda: 'Not Found') will return 'Not Found' for missing 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.