How does collections.defaultdict work?

Question

I\'ve read the examples in python docs, but still can\'t figure out what this method means. Can somebody help? Here are two examples from the python docs

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Answer 1

The documentation and the explanation are pretty much self-explanatory:

http://docs.python.org/library/collections.html#collections.defaultdict

The type function(int/str etc.) passed as an argument is used to initialize a default value for any given key where the key is not present in the dict.