Python: Check if one dictionary is a subset of another larger dictionary

Question

I'm trying to write a custom filter method that takes an arbitrary number of kwargs and returns a list containing the elements of a database-like list that contain those kwargs.

For example, suppose d1 = {'a':'2', 'b':'3'} and d2 = the same thing. d1 == d2 results in True. But suppose d2 = the same thing plus a bunch of other things. My method needs to be able to tell if d1 in d2, but Python can't do that with dictionaries.

Context:

I have a Word class, and each object has properties like word, definition, part_of_speech, and so on. I want to be able to call a filter method on the main list of these words, like Word.objects.filter(word='jump', part_of_speech='verb-intransitive'). I can't figure out how to manage these keys and values at the same time. But this could have larger functionality outside this context for other people.

Answer 1

In Python 3, you can use dict.items() to get a set-like view of the dict items. You can then use the <= operator to test if one view is a "subset" of the other:

d1.items() <= d2.items()

In Python 2.7, use the dict.viewitems() to do the same:

d1.viewitems() <= d2.viewitems()

In Python 2.6 and below you will need a different solution, such as using all():

all(key in d2 and d2[key] == d1[key] for key in d1)