Re: Extract Indices of Numpy Array Based on Given Bit Information

References	<CA+F4vi=SMCNO-v55ZyKBau6+HAt=HPRYECnVkUr28wzgG3praA@mail.gmail.com> <CAPTjJmohbdOOn_Ug1iYBJO6NMoR944OY+ecUCamGO26hTNZEcA@mail.gmail.com> <CA+F4vinwQvNJWu2wkx_sr+xhTWJOvXtODb9PZH9vvYbSCG+1iQ@mail.gmail.com>
Date	2014-10-18 17:50 +1100
Subject	Re: Extract Indices of Numpy Array Based on Given Bit Information
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.14958.1413615055.18130.python-list@python.org> (permalink)

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On Sat, Oct 18, 2014 at 5:42 PM, Artur Bercik <vbubbly21@gmail.com> wrote:
> I got some sense, but could not imagine if required Bit No. 2–5, and  Bit
> Combination 0000.
>
> I hope example with the new case would make me more sense.
>

Just write the number in binary, with the bits you're interested in
set to 1, and everything else 0:

... 876543210
... 000111100

>>> 0b000111100
60
>>> 1073741877 & 0b000111100
52

So this number does _not_ have all zeroes there. If it did, the result
would be zero. To look for some other pattern, just do the same thing
- suppose we want to find numbers where it's 1001, we just look for
the result to be 0b000100100, or 36.

ChrisA

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Re: Extract Indices of Numpy Array Based on Given Bit Information Chris Angelico <rosuav@gmail.com> - 2014-10-18 17:50 +1100

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