Question

I would like to loop through two lists of lists and avoid duplicate combinations of values between positions 1 and 2 of each list.

a = [[2007, 206, 205, 8], [2007, 206, 208, 9]]
b = [[2007, 205, 206, 8], [2007, 207, 210, 10]]

In this case for a[0], positions 1 and 2 would be 206 and 205 respectively, and for b[0], positions 1 and 2 would be 205 and 206. a[0] and b[0] derive from the same data set, but are structured differently. However, b[0] would be a duplicate of a[0] based on the combination. How do I avoid having this combination-based duplicate?

Thank you.

Answer 1

If you want a result of something like:

c = [[2007, 206, 205, 8], [2007, 206, 208, 9], [2007, 207, 210, 10]]

That should be easy enough:

a = [[2007, 206, 205, 8], [2007, 206, 208, 9]]
b = [[2007, 205, 206, 8], [2007, 207, 210, 10]]
from itertools import chain
seen = set()
c = []
for lst in chain(a,b):
    one_two = tuple(lst[:1] + sorted(lst[1:-1]) + lst[-1:])
    if one_two not in seen:
       seen.add(one_two)
       c.append(lst)