Finding the intersection of nested lists in Python?

Question

def query_RR(postings, qtext): 
words = tokenize(qtext) 
allpostings = [postings[w] for w in words]
for a in allpostings: 
print a.keys()

And this was the result of the query [0, 2, 3, 4, 6] [1, 4, 5] [0, 2, 4] [4, 5]

The query is taking a user inputted term ('qtext'), tokenizing and generating a postings list for each token.

The posting list is a list of nested dictionaries (e.g. [{0 : 0.68426, 1: 0.26423}, {2: 0.6842332, 0: 0.9823}]. I am attempting to find the intersection for these nested dictionaries using the keys

Answer 1

Assuming the order does not matter, you could use set.intersection():

>>> lst = [[0, 2, 3, 4, 6], [1, 4, 5], [0, 2, 4], [4, 5]]
>>> set.intersection(*map(set,lst))
{4}
>>> set(lst[0]).intersection(*lst[1:])
{4}