[Numpy-discussion] Re: Ransom Proposals

Robert Kern robert.kern at gmail.com
Mon Mar 27 15:52:06 CST 2006


Travis Oliphant wrote:
> Tim Hochberg wrote:
> 
>>> Charles R Harris wrote:
>>>
>>>     >>> l = list(a)
>>>     >>> l
>>>    [999, 1, 2, 3, 4, 5, 6, 7, 8]
>>>     >>> a
>>>    array([999,   1,   2,   3,   4,   5,   6,   7,   8])
>>>     >>> l += a
>>>     >>> l
>>>    array([1998,    2,    4,    6,    8,   10,   12,   14,   16])
>>>     >>> a
>>>    array([999,   1,   2,   3,   4,   5,   6,   7,   8])
>>
>> Let me add that I think that this is pretty dubious, so if this is a
>> new feature, perhaps we should revert it before it becomes entrenched.
> 
> I don't think it's a new feature, but it's simply the result of
> 
> l += a being translated to
> 
> l = l + a  # lists don't have in-place add's
> 
> Numeric has this behavior as well.

Lists do have in-place adds.

In [1]: a = range(10)

In [2]: b = range(10, 20)

In [3]: id(a)
Out[3]: 92350264

In [4]: a += b

In [5]: id(a)
Out[5]: 92350264

In [6]: a
Out[6]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

-- 
Robert Kern
robert.kern at gmail.com

"I have come to believe that the whole world is an enigma, a harmless enigma
 that is made terrible by our own mad attempt to interpret it as though it had
 an underlying truth."
  -- Umberto Eco





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