python - How to find elements that are common to all lists in a nested list?

Question

I have a large nested list and each list within the nested list contains a list of numbers that are formatted as floats. However every individual list in the nested list is the same except for a few exceptions. I want to extract the numbers that are common to all of the lists in the nested list. A simple example of my problem is shown below:

nested_list = [[1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0],
              [2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0],
              [1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0],
              [2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0,15.0]]

In the following case I would want to extract the following:

common_vals = [2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0,13.0,14.0]

I tried to use set intersections to solve this but since I wasn't able to get this to work on all of the elements of the nested list.

Answer 1

Try this, it's the simplest solution:

set.intersection(*map(set, nested_list))

Or if you prefer to use generator expressions, which should be a more efficient solution in terms of memory usage:

set.intersection(*(set(e) for e in nested_list))