[SciPy-user] Manipulating Bit-Masked Data

Dave Kuhlman dkuhlman at cutter.rexx.com
Tue Dec 27 22:18:19 CST 2005


On Tue, Dec 27, 2005 at 04:55:47PM -0800, Rich Shepard wrote:
>    I need to read bit-masked bytes from an Optical Mark Recognition card
> reader. I'm quite new to Python and haven't found any documentation on how to
> manipulate bits. NumPy has masked arrays, but that's a different situation.
> My rummaging around the SciPy wiki and a search of the mail list archives
> turned up nothing.
> 
>    I'd appreciate a pointer to documentation that will show me how to
> manipulate bit-masks in Python.

Define your hex masks with things like 0x1f.  See:
http://docs.python.org/ref/integers.html.

And, I believe, the bit-wise operators you want are "&", "^", and
"|" (and, xor, and or).  See:
http://docs.python.org/ref/bitwise.html.

Also, the built-in functions ord() and hex() may be useful.  See:
http://docs.python.org/lib/built-in-funcs.html.

If you need lots of speed while doing this, you may want to look into
Pyrex.  But, that's an advanced topic.

Hope this helps.

Dave


-- 
Dave Kuhlman
http://www.rexx.com/~dkuhlman



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