How to check if one dictionary is a subset of another larger dictionary?

178

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.

Edit Report

1 Answer

>>> d1 = {'a':'2', 'b':'3'}
>>> d2 = {'a':'2', 'b':'3','c':'4'}
>>> all((k in d2 and d2[k]==v) for k,v in d1.iteritems())
True

context:

>>> d1 = {'a':'2', 'b':'3'}
>>> d2 = {'a':'2', 'b':'3','c':'4'}
>>> list(d1.iteritems())
[('a', '2'), ('b', '3')]
>>> [(k,v) for k,v in d1.iteritems()]
[('a', '2'), ('b', '3')]
>>> k,v = ('a','2')
>>> k
'a'
>>> v
'2'
>>> k in d2
True
>>> d2[k]
'2'
>>> k in d2 and d2[k]==v
True
>>> [(k in d2 and d2[k]==v) for k,v in d1.iteritems()]
[True, True]
>>> ((k in d2 and d2[k]==v) for k,v in d1.iteritems())
<generator object <genexpr> at 0x02A9D2B0>
>>> ((k in d2 and d2[k]==v) for k,v in d1.iteritems()).next()
True
>>> all((k in d2 and d2[k]==v) for k,v in d1.iteritems())
True
>>>

answered 2012-02-17T06:30:13.910

How to check if one dictionary is a subset of another larger dictionary?

1 Answer

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