TP於 2012年9月27日星期四UTC+8上午5時25分04秒寫道：
> Hi everybody,
>
>
>
> I have tried, naively, to do the following, so as to make lists quickly:
>
>
>
> >>> a=[0]*2
>
> >>> a
>
> [0, 0]
>
> >>> a[0]=3
>
> >>> a
>
> [3, 0]
>
>
>
> All is working fine, so I extended the technique to do:
>
>
>
> >>> a=[[0]*3]*2
>
> >>> a
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> [[0, 0, 0], [0, 0, 0]]
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> >>> a[0][0]=2
>
> >>> a
>
> [[2, 0, 0], [2, 0, 0]]
>
>
>
> The behavior is no more expected!
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> The reason is probably that in the first case, 0 is an integer, not a list,
>
> so Python copies two elements that are independent.
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> In the second case, the elements are [0,0,0], which is a list; when Python
>
> copies a list, he copies in fact the *pointer* to the list, such that we
>
> obtain this apparently strange behavior.
>
>
>
> Is it the correct explanation?
>
> In these conditions, how to make this list [[0,0,0],[0,0,0]] with "*"
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> without this behavior?
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>
>
> Thanks,
>
>
>
> TP
def zeros(m,n):
for i in xrange(m):
for j in xrange(n):
a[i][j]=0
return a
>>> a=zeros(3,2)
>>> a
[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]]
>>>
I think this is what you want.
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