Generating circular shifts / reduced Latin Squares in Python

Question

Was just wondering what\'s the most efficient way of generating all the circular shifts of a list in Python. In either direction. For example, given a list [1, 2, 3, 4

Answer 1

For the first part, the most concise way probably is

a = [1, 2, 3, 4]
n = len(a)
[[a[i - j] for i in range(n)] for j in range(n)]
# [[1, 2, 3, 4], [4, 1, 2, 3], [3, 4, 1, 2], [2, 3, 4, 1]]

and for the second part

[[a[i - j] for i in range(n)] for j in range(n, 0, -1)]
# [[1, 2, 3, 4], [2, 3, 4, 1], [3, 4, 1, 2], [4, 1, 2, 3]]

These should also be much more efficient than your code, though I did not do any timings.