Re: [Numpy-discussion] how to set a fixed sized dtype suitable for bitwise operations
On Tue, Apr 28, 2015 at 7:00 AM, Benjamin Root ben.r...@ou.edu wrote:
I have a need to have a numpy array of 17 byte (more specifically, at
least 147 bits) values that I would be doing some bit twiddling on. I have
found that doing a dtype of i17 yields a dtype of int32, which is
completely not what I intended. Doing 'u17' gets an data type not
understood. I have tried 'a17', but then bitwise_or() and left_shift() do
not work (returns NotImplemented).
How should I be going about this?
The correct type to use would be a void dtype:
dt = np.dtype('V17')
dt.itemsize
17
Unfortunately, it does not support bitwise operations either, which seems
like an oddity to me:
a = np.empty(2, dt)
a[0] = 'abcdef'
a[1] = bytearray([64, 56, 78])
a[0] | a[1]
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: unsupported operand type(s) for |: 'numpy.void' and 'numpy.void'
Any fundamental reason for this?
Jaime
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[Numpy-discussion] how to set a fixed sized dtype suitable for bitwise operations
I have a need to have a numpy array of 17 byte (more specifically, at least 147 bits) values that I would be doing some bit twiddling on. I have found that doing a dtype of i17 yields a dtype of int32, which is completely not what I intended. Doing 'u17' gets an data type not understood. I have tried 'a17', but then bitwise_or() and left_shift() do not work (returns NotImplemented). How should I be going about this? Cheers! Ben Root ___ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] how to set a fixed sized dtype suitable for bitwise operations
Yeah, I am not seeing any way around it at the moment. I guess I will have
to use the bitarray package for now. I was hoping for some fast per-element
processing, but at the moment, I guess I will have to sacrifice that just
to have something that worked correctly.
Ben Root
On Tue, Apr 28, 2015 at 10:19 AM, Jaime Fernández del Río
jaime.f...@gmail.com wrote:
On Tue, Apr 28, 2015 at 7:00 AM, Benjamin Root ben.r...@ou.edu wrote:
I have a need to have a numpy array of 17 byte (more specifically, at
least 147 bits) values that I would be doing some bit twiddling on. I have
found that doing a dtype of i17 yields a dtype of int32, which is
completely not what I intended. Doing 'u17' gets an data type not
understood. I have tried 'a17', but then bitwise_or() and left_shift() do
not work (returns NotImplemented).
How should I be going about this?
The correct type to use would be a void dtype:
dt = np.dtype('V17')
dt.itemsize
17
Unfortunately, it does not support bitwise operations either, which seems
like an oddity to me:
a = np.empty(2, dt)
a[0] = 'abcdef'
a[1] = bytearray([64, 56, 78])
a[0] | a[1]
Traceback (most recent call last):
File stdin, line 1, in module
TypeError: unsupported operand type(s) for |: 'numpy.void' and 'numpy.void'
Any fundamental reason for this?
Jaime
--
(\__/)
( O.o)
( ) Este es Conejo. Copia a Conejo en tu firma y ayúdale en sus planes
de dominación mundial.
___
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NumPy-Discussion@scipy.org
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