The defaultdict tool is a container in the collections class of Python. It's similar to the usual dictionary (dict) container, but it has one difference: The value fields' data type is specified upon initialization.

Jan 4, 2017 · From the documentation of defaultdict: If default_factory is not None, it is called without arguments to provide a default value for the given key, this value is inserted in the dictionary for the …

The argument to defaultdict should be a function. defaultdict(int) is a dictionary, while lambda: defaultdict(int) is function that returns a dictionary.

Asides from the ergonomics of having .get everwhere, one important difference is if you lookup a missing key in defaultdict it will insert a new element into itself rather than just returning the default.

Jul 5, 2011 · dict and collections.defaultdict are both very completely defined in the documentation. What specific questions do you have about the actual words used in the actual documentation?

The second argument, ht is optional and refers to the base dictionary that the new defaultdict will be built on. Therefore, if ht had some keys and values, the defaultdict would also have these keys with the …

Apr 19, 2015 · 121 If I have d=dict(zip(range(1,10),range(50,61))) how can I build a collections.defaultdict out of the dict? The only argument defaultdict seems to take is the factory …

Apr 8, 2010 · 202 Thanks to some great folks on SO, I discovered the possibilities offered by collections.defaultdict, notably in readability and speed. I have put them to use with success. Now I …

Mar 18, 2021 · I saw someone use defaultdict(set) to solve a problem after importing it from collections, but it was in passing so I didn't get to look at the problem fully. I know if you do defaultdict(int) then...

Note this is asking how to do an infinite-level recursive defaultdict, so it's distinct to Python: defaultdict of defaultdict?, which was how to do a two-level defaultdict.