[Numpy-discussion] unpacking data values into array of bits

[R Schumacher]

Hmmm
np.unpackbits (np.array (memoryview(struct.pack ('d', 
np.pi)))).astype(np.int32)
np.array([b for b in np.binary_repr(314159)], 'int32') # ints only!
np.array([b for b in 
bin(struct.unpack('!i',struct.pack('!f',1.0))[0])[2:]], 'int32')

timing is untested.

- Ray Schumacher


At 07:22 AM 2/12/2015, you wrote:
>Robert Kern wrote:
>
> > On Thu, Feb 12, 2015 at 3:00 PM, Neal Becker <ndbecker2 at gmail.com> wrote:
> >>
> >> Robert Kern wrote:
> >>
> >> > On Thu, Feb 12, 2015 at 2:21 PM, Neal Becker <ndbecker2 at gmail.com>
> > wrote:
> >> >>
> >> >> I need to transmit some data values.  These values will be float and
> > long
> >> >> values.  I need them encoded into a string of bits.
> >> >>
> >> >> The only way I found so far to do this seems rather roundabout:
> >> >>
> >> >>
> >> >> np.unpackbits (np.array (memoryview(struct.pack ('d', pi))))
> >> >> Out[45]:
> >> >> array([0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 0,
> > 1,
> >> > 0,
> >> >>        0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0,
> > 0,
> >> > 0,
> >> >>        0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0],
> > dtype=uint8)
> >> >>
> >> >> (which I'm not certain is correct)
> >> >>
> >> >> Also, I don't know how to reverse this process
> >> >
> >> > You already had your string ready for transmission with
> > `struct.pack('d',
> >> > pi)`.
> >> >
> >> > --
> >> > Robert Kern
> >>
> >> my transmitter wants an np array of bits, not a string
> >
> > Can you provide any details on what your "transmitter" is?
> >
> > --
>
>My transmitter is c++ code that accepts as input a numpy array of np.int32.
>Each element of that array has value 0 or 1.
>
>
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