Python - 在字典中查找值的交集

Question

Im writing a function to handle multiple queries in a boolean AND search. I have a dict of docs where each query occurs= query_dict

I want the intersection of all values in the query_dict.values():

query_dict = {'foo': ['doc_one.txt', 'doc_two.txt', 'doc_three.txt'],
              'bar': ['doc_one.txt', 'doc_two.txt'],
              'foobar': ['doc_two.txt']}

intersect(query_dict)

>> doc_two.txt

I've been reading about intersection but I'm finding it hard to apply it to a dict.

Thanks for your help!

Answer 1

In [36]: query_dict = {'foo': ['doc_one.txt', 'doc_two.txt', 'doc_three.txt'],
              'bar': ['doc_one.txt', 'doc_two.txt'],
              'foobar': ['doc_two.txt']}

In [37]: reduce(set.intersection, (set(val) for val in query_dict.values()))
Out[37]: set(['doc_two.txt'])

In [41]: query_dict = {'foo': ['doc_one.txt', 'doc_two.txt', 'doc_three.txt'], 'bar': ['doc_one.txt', 'doc_two.txt'], 'foobar': ['doc_two.txt']}

set.intersection(*(set(val) for val in query_dict.values())) is also a valid solution, though it's a bit slower:

In [42]: %timeit reduce(set.intersection, (set(val) for val in query_dict.values()))
100000 loops, best of 3: 2.78 us per loop

In [43]: %timeit set.intersection(*(set(val) for val in query_dict.values()))
100000 loops, best of 3: 3.28 us per loop

Answer 2

Another way

first = query_dict.values()[0]
rest = query_dict.values()[1:]
print [t for t in set(first) if all(t in q for q in rest)]