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

Well, defaultdict can also raise keyerror in the following case:

    from collections import defaultdict
    d = defaultdict()
    print(d[3]) #raises keyerror

Always remember to give argument to the defaultdict like defaultdict(int).