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edited Mar 31, 2017 at 19:20

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I usually use a defaultdict for situations like this. You supply a factory method that takes no arguments and creates a value when it sees a new key. It's more useful when you want to return something like an empty list on new keys (see the examples).

from collections import defaultdict d = defaultdict(lambda : None) print d['new_key'] #prints # prints 'None'

I usually use a defaultdict for situations like this. You supply a factory method that takes no arguments and creates a value when it sees a new key. It's more useful when you want to return something like an empty list on new keys (see the examples).

from collections import defaultdict d = defaultdict(lambda : None) print d['new_key'] #prints 'None'

I usually use a defaultdict for situations like this. You supply a factory method that takes no arguments and creates a value when it sees a new key. It's more useful when you want to return something like an empty list on new keys (see the examples).

from collections import defaultdict d = defaultdict(lambda: None) print d['new_key']  # prints 'None'

answered May 25, 2011 at 21:09

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I usually use a defaultdict for situations like this. You supply a factory method that takes no arguments and creates a value when it sees a new key. It's more useful when you want to return something like an empty list on new keys (see the examples).

from collections import defaultdict d = defaultdict(lambda : None) print d['new_key'] #prints 'None'