[issue26751] Possible bug in sorting algorithm

[Benjamin Peterson]

Changes by Benjamin Peterson :


--
resolution:  -> not a bug
status: open -> closed

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[issue26751] Possible bug in sorting algorithm

[Tim Peters]

Tim Peters added the comment:

If that's the actual code you're using, it has a bug:  the "if k2[1] is None" 
test is useless, since regardless of whether it's true or false, the next `if` 
suite overwrites `retval`.  You probably meant

elif k1[1] ...
^^

instead of

if k1[1] ...

Does that fix your problem?

If not, please augment the bug report with the _complete_ code you're actually 
using, a sample problematic input, the exact output you're expecting, and the 
exact output you're seeing instead.  We're not telepathic ;-)

--
nosy: +tim.peters

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[issue26751] Possible bug in sorting algorithm

[David Manowitz]

New submission from David Manowitz:

I'm trying to sort a list of tuples.  Most of the tuples are pairs of US state 
names.  However, some of the tuples have None instead of the 2nd name.  I want 
the items sorted first by the 1st element, and then by the 2nd element, BUT I 
want the None to count as LARGER than any name.  Thus, I want to see 
[('Alabama', 'Iowa'), ('Alabama', None)] rather than [('Alabama', None), 
('Alabama', 'Iowa')].  I defined the following comparitor:

def cmp_keys (k1, k2):
retval = cmp(k1[0], k2[0])
if retval == 0:
if k2[1] is None:
retval = -1
if k1[1] is None:
retval = 1
else:
retval = cmp(k1[1], k2[1])

return retval

However, once I sort using this, some of the elements are out of order.

--
components: Interpreter Core
messages: 263367
nosy: David.Manowitz
priority: normal
severity: normal
status: open
title: Possible bug in sorting algorithm
type: behavior
versions: Python 2.7

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