[Numpy-discussion] dtype and array creation

[josef.pktd at gmail.com]

On Thu, May 20, 2010 at 4:04 PM, Keith Goodman <kwgoodman at gmail.com> wrote:
> Why do the follow expressions give different dtype?
>
>>> np.array([1, 2, 3], dtype=str)
> array(['1', '2', '3'],
>      dtype='|S1')
>>> np.array(np.array([1, 2, 3]), dtype=str)
> array(['1', '2', '3'],
>      dtype='|S8')

you're on a 64bit machine?

S8 is the same size as the float


>>> np.array([8]).itemsize
4
>>> np.array(np.array([1, 2, 3]), dtype=str)
array(['1', '2', '3'],
      dtype='|S4')
>>> np.array([8]).view(dtype='S4')
array(['\x08'],
      dtype='|S4')
>>> np.array([8]).view(dtype='S1')
array(['\x08', '', '', ''],
      dtype='|S1')

But I don't know whether this is a desired feature, numpy might reuse
the existing buffer (?)

Josef


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