Python -Intersection of multiple lists?

user_184046 0
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I am playing with python and am able to get the intersection of two lists:

result = set(a).intersection(b)

Now if d is a list containing a and b and a third element c, is there an built-in function for finding the intersection of all the three lists inside d? So for instance,

d = [[1,2,3,4], [2,3,4], [3,4,5,6,7]]

then the result should be

[3,4]
intersection set list python
6 Answers

@user3917838

Nice and simple but needs some casting to make it work and give a list as a result. It should look like:

list(reduce(set.intersection, [set(item) for item in d ]))

where:

d = [[1,2,3,4], [2,3,4], [3,4,5,6,7]]

And result is:

[3, 4]

At least in Python 3.4

user_70067330

You can get the intersection of an arbitrary number sets using set.intersection(set1, set2, set3...). So you just need to convert your lists into sets and then pass them to this method as follows: 

d = [[1,2,3,4], [2,3,4], [3,4,5,6,7]]  
set.intersection(*[set(x) for x in d])

result: 

{3, 4}
user_122605240

I find reduce() to be particularly useful. In fact, the numpy documents recommend using reduce() to intersect multiple lists: numpy.intersect1d reference

To answer your question:

import numpy as np
from functools import reduce
# apply intersect1d to (a list of) multiple lists:
reduce(np.intersect1d, [list_1, list_2, ... list_n])
user_91580750
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