Python 2.7动态长度列表理解

Question

I apologize in advance if this question has already been answered. I have done my best to search for a solution with my limited knowledge of terminology.

This is the line of code in question:

Matrix = list([s0, s1, s2] for s0 in splits[0] for s1 in splits[1] for s2 in splits[2])

Basically, I'm constructing a list (Matrix) with all permutations in the list of lists, "Splits". However, Splits is not always the same size. For instance, sometimes there are 4 columns and the line would look like this:

 Matrix = list([s0, s1, s2, **s3**] for s0 in splits[0] for s1 in splits[1] for s2 in splits[2] **for s3 in splits[3]**)

How can I make this line adaptive to the length of Splits? Ie

Matrix = list([s0,s1... , sN] for s0 in splits[0] for s1 in splits[1] ... for sN in splits[N])

Thank you

Answer 1

Unpack splits into the arguments to itertools.product :

from itertools import product

splits = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# Note: a list of tuples, because product yields tuples
explicit = list((s0, s1, s2) for s0 in splits[0] for s1 in splits[1] for s2 in splits[2])

unpacking = list(product(*splits))

assert explicit == unpacking