Eric Eisner wrote:
Hello,
As previously mentioned on python-ideas [1] (circa 2006), it would make sense to be able to perform bitwise operations on bytes/bytearray.
Stealing the example from the original suggestion:
Suppose I have a string (say, read in from a binary file) that has a 4-byte field in it. Bit 11 indicates whether the accompanying data is in glorped form (something I'm just making up for this example).
For example, if the field has 0x000480c4, the data is not glorped. If the data is glorped, bit 11 would be on, i.e., 0x001480c4.
Let's say I want to turn on the glorp bit; what I have to do now:
GLORPED = 0x10 newchar = flags[1] | GLORPED flags = flags[0] + newchar + flags[2:]
What I'd like to be able to do is something like:
GLORPED = b"\x00\x10\x00\x00" flags |= GLORPED
You can already do bitwise operations on bytes, and retrieving the relevant byte and using single-byte operations on it is simple enough. As I see it, the major underlying problem here is that byte-arrays are immutable, since what you really want is to be able to change a single byte of the array in-place. In general, Python's byte arrays and strings are very ill suited for dealing with data which isn't byte-based, and definitely horrible at building or modifying data streams. I recommend using an external library for working with data structures and/or data streams. Construct[1] is my personal favorite, since it's especially Pythonic and easy to use. In any case, if you wish to propose a mutable byte/bit array which supports array-wise binary operators, I can say I would certainly be glad to have such a class at my disposal. - Tal [1] http://construct.wikispaces.com/