Python "why" questions
robert.kern at gmail.com
Tue Aug 17 17:22:27 CEST 2010
On 8/16/10 11:10 PM, Steven D'Aprano wrote:
> On Mon, 16 Aug 2010 22:56:20 -0500, Robert Kern wrote:
>> On 8/16/10 9:29 PM, Roy Smith wrote:
>>> In article<i4cqg0$olf$3 at lust.ihug.co.nz>,
>>> Lawrence D'Oliveiro<ldo at geek-central.gen.new_zealand> wrote:
>>>> In message<roy-EE1B7F.21001716082010 at news.panix.com>, Roy Smith wrote:
>>>>> 5) real intensity[160.0 : 30.0 : 0.01]
>>>> How many elements in that array?
>>>> a) 2999
>>>> b) 3000
>>>> c) neither of the above
>>> c) neither of the above. More specifically, 13,001 (if I counted
>> 13000, actually. Floating point is a bitch.
>> |1> import numpy
>> |2> len(numpy.r_[160.0:30.0:-0.01])
> Actually, the answer is 0, not 13000, because the step size is given as
> 0.01, not -0.01.
>>>> import numpy
Roy wasn't using numpy/Python semantics but made-up semantics (following Martin
Gregorie's made-up semantics to which he was replying) which treat the step size
as a true size, not a size and direction. The direction is determined from the
start and stop parameters. It's an almost-reasonable design.
"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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