Anonymous user
Talk:Spiral matrix: Difference between revisions
→Python array initialisation edit problem
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:--[[User:Paddy3118|Paddy3118]] 16:56, 5 August 2008 (UTC)
::This one includes a sort, too :) That's one of the neatest parts! Alright, let me write out the algo real quick (I'll gloss over details and may fib a bit, to get the idea across quickly).
== Python array initialisation edit problem ==
Hi Spoon, your edit to Spiral of substituting <python>array = [[None]*n]*n</python> for <python>array = [[None]*n for j in range(n)]</python> [[http://www.rosettacode.org/w/index.php?title=Spiral&curid=2967&diff=16906&oldid=16746 here]] doesn't work because of:
<python>>>> n=2
>>> a = [[None]*n]*n
>>> a
[[None, None], [None, None]]
>>> a[0][0] = 1
>>> a
[[1, None], [1, None]]
>>></python>
You are referencing the inner list multiple times instead of creating new copies. --[[User:Paddy3118|Paddy3118]] 06:17, 14 August 2008 (UTC)
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