Defaultdict

Defining a Defaultdict

A defaultdict almost behaves the same as a dictionary
If a user attempts to access a missing key:
- A dictionary will throw a KeyError
- A defaultdict will create an item using a default value
This is one of the only differences between the two

Differentiating between `dict` and `defaultdict`

>>> d = {}
>>> d['hello']
KeyError: 'hello'

>>> from collections import defaultdict
>>> dd = defaultdict(int)
>>> dd['hello']
0
>>> print(dd)
defaultdict(<class 'int'>, {'hello': 0})
>>> print(dd['hello'])
0

Initializing a Defaultdict

>>> from collections import defaultdict
>>> dd = defaultdict(int)
>>> print(dd)
defaultdict(<class 'int'>, {})

Adding to a Defaultdict

>>> from collections import defaultdict
>>> dd = defaultdict(list)
>>> dd['hello']
[]
>>> print(dd)
defaultdict(<class 'list'>, {'hello': []})

References

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