Getting at the bits of a 32-bit integer

Grant Edwards grante at visi.com
Tue Aug 24 03:25:09 CEST 2004


On 2004-08-24, Jeremy Bowers <jerf at jerf.org> wrote:

>>>> a = 1023
>>>> (a & 1024) >> 10
> 0
>
> Obviously, you need better constants and stuff.
>
> However, I must challenge your need to do this in the first place.

That's a bit, um, conceited.  Somebody's got to twiddle all
those low-level bits out there to provide the infrastructure
that makes the world run.

I'm one of those people, and I need to do bit-twiddling quite
often while implimenting various communications protocols.

> Python and bit twiddling generally don't go together;

Says you.  I say they go together quite well.  Bit-twiddling in
Python works great.  It's a hell of a lot easier than doing it
in C, and I've switched to Python for all my non-embedded
bit-twiddling needs.

> even if you are accessing a binary file or protocol you should
> shuffle out as much to the struct (?) module as possible.

Struct only works at the byte level.  For bitfields within
bytes, you've got to use the bitwise and/or/xor/shift operators
just like you do in C.

> If you want to track every bit and byte, Python is the wrong
> language for you...

So, what language do you think is better?  It sure isn't C. I
did bit-twiddling in C for 20 years, and doing it in Python is
much easier.

> and unless you are tracking many many millions of bits, this
> is the wrong decade for it.

I guess I plain don't understand that last clause.  It seems to
imply that if you _are_ tracking many millions of bits, this is
the decade to do it in Python?

I used C for many, many years for low-level stuff like tearing
apart serial data streams, Ethernet frames, IP headers and
suchlike, and I can assure you that it's far, far easier to do
stuff like that in Python than in C.

-- 
Grant Edwards                   grante             Yow!  Where's SANDY DUNCAN?
                                  at               
                               visi.com            



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