Hi Martin, thanks for the response, please see below.
On 29/05/2010 20:12, Martin Manns wrote:
On Sat, 29 May 2010 19:46:28 +0100
Mark Lawrence<breamore...@yahoo.co.uk> wrote:
I've had an OverflowError using xrange with Python 2.6.5 on Windows.
Googling got me to the subject line.
msg97928 gives a code snippet to overcome the limitations of xrange,
allowing for negative steps, however it doesn't raise a ValueError
for a zero step. msg99624 gives a docs change that has been
implemented for V2.6, but this doesn't refer to the msg97928 code
snippet, rather it refers to a one liner that only works for positive
steps. The docs for V2.7 haven't been changed at all.
Mark:
Thank you for posting.
2.7 is not affected by issue 7721 because itertools.islice behavior is
changed. Therefore, the original snippet should work in 2.7 (I have not
tested this).
From http://docs.python.org/dev/library/itertools.html
"Unlike regular slicing, islice() does not support negative values for
start, stop, or step."
Rule 1 of programming never assume anything, particularly wrt testing. I
assume that you are ok with this. :) Dreadful I know :)
I found the msg97928 code pretty obvious when seeing the snippet.
If you disagree you may consider re-opening the issue.
Try running this on Python 2.6.5 in file irange.py
from itertools import takewhile, count
def irange(start, stop, step):
if step < 0:
cond = lambda x: x > stop
else:
cond = lambda x: x < stop
return takewhile(cond, (start + i * step for i in count()))
if __name__=='__main__':
for i in irange(0, 10, 0): print i
My output from the command line
c:\Users\Mark\python>irange
0
0
etc etc etc
I trust that you get my point regarding the failure to raise a
ValueError :) Or am I wearing my extremely stupid hat today?
Martin
Kindest regards.
Mark Lawrence.
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