Getting at the bits of a 32-bit integer

Paul Rubin http
Tue Aug 24 02:16:31 CEST 2004


jacobsmail at postmark.net (Jacob H) writes:
> There are plenty of unused bits to the left of the number itself. If I
> wanted to use some of these bits as true/false flags, how would I go
> about it? In Python, how do I write code that gets at the leftmost
> byte, or the third bit from the left of the set of 32, or the
> rightmost byte plus the bit to its left, etc...

It's not really in the Python spirit, but in general you can set the
nth bit (from the right, starting at n=0) of variable x by saying:

   x |= (1 << n)

You can clear it with

  x &= ~(1 << n)

and you can test it with

   if x & (1 << n):
     do whatever



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