I have a list of sublists. I need all possible pairs between the elements in the sublists. For example, for a list like this:

a=[[1,2,3],[4,5],[6]]

The result should be:

result=[[1,4], [1,5], [1,6], [2,4], [2,5], [2,6], [3,4], [3,5], [3,6], [4,6], [5,6]]

The lists (and sublists) are of various, random lengths.

You can do the following

>>> from itertools import chain
>>> a=[[1,2,3],[4,5],[6]]
>>> b=[]
>>> for index, item in enumerate(a):
...    b.extend([[i, j] for i in item for j in chain.from_iterable(a[index+1:])])
>>> b
[[1, 4],[1, 5],[1, 6],[2, 4],[2, 5],[2, 6],[3, 4],[3, 5],[3, 6],[4, 6],[5, 6]]