[Numpy-discussion] Oddity with numpy.int64 integer division

Christian Marquardt christian@marquardt...
Mon Apr 23 15:29:00 CDT 2007


Actually,

it happens for normal integers as well:

   >>> n = np.array([-5, -100, -150])
   >>> n // 100
   array([ 0, -1, -1])
   >>> -5//100, -100//100, -150//100
   (-1, -1, -2)

On Mon, April 23, 2007 22:20, Christian Marquardt wrote:
> Dear all,
>
> this is odd:
>
>    >>> import numpy as np
>    >>> fact = 28250000L * 86400L
>    >>> nn = np.array([-20905000L])
>    >>> nn
>    array([-20905000], dtype=int64)
>    >>> nn[0] // fact
>    0
>
> But:
>
>    >>> long(nn[0]) // fact
>    -1L
>
> Is this a bug in numpy, or in python's implementation of longs? I would
> think both should give the same, really... (Python 2.5, numpy
> 1.0.3dev3725,
> Linux, Intel compilers...)
>
> Many thanks for any ideas / advice,
>
>   Christian
>
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