Hi folks,
I am trying to cyclically rotate a seq until it reached the beginning stage again.
I would like to be able to rotate in both directions and using any arbitrary interval.
I think the code is correct but I have a few suggestions below.
#!/usr/bin/env python
import sys import random
If you make these comments into a docstring (a triple-quoted string that starts the method) then they will be accessible to IDEs, help(rotate), etc.
# cyclically rotate a sequence # -- -------------------------------------------------------- # should work on any sequence type # should work with any hop(n) interval # should also work in both directions (left or right) # -- --------------------------------------------------------
def rotate(seq, n=1): if len(seq) == 0: return seq
I would also check for seq == None. An easy way to check for both None and an empty sequence is if not seq: return seq
This will reject also a few other things you probably don't care about such as the number 0 and an empty dict...
# Normalize n, using modulo - even works for negative n n = n % len(seq) return seq[n:] + seq[:n]
def test():
start = 1
x = [7, 2, 1, 0, 11, 6, 5, 4]
print; print x; print '--' * 8
for i in range(len(x)):
If you use for i in range(1, len(x)+1) then you don't need start, i will have the same value
out = rotate(x, start)
print out
start = start + 1
Your test is not nearly as thorough as your docs suggest. You don't test rotation by a negative number or by a number bigger than len(x).
You might want to write this as a unittest so the results are checked automatically instead of you having to eyeball them each time. Here is a start:
import unittest
class RotateTest(unittest.TestCase):
def test_rotate(self):
x = [7, 2, 1, 0, 11, 6, 5, 4]
out = rotate(x, 1)
self.assertEquals([2, 1, 0, 11, 6, 5, 4, 7], out) out = rotate(x, -1)
self.assertEquals([4, 7, 2, 1, 0, 11, 6, 5], out)if __name__ == '__main__':
unittest.main()
Kent
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