hi i am reading in byte array/list from socket... but now i want python to treat the first byte as "unsigned 8 bit integer". how is this possible? and how is it possible to get its integer value as unsigned 8 bit integer?
thanks in advance!
+1
A:
bytes/bytearray is a sequence of integers. If you just access an element by its index you'll have an integer:
>>> b'abc'
b'abc'
>>> _[0]
97
By their very definition, bytes and bytearrays contain integers in the range(0, 256). So they're "unsigned 8-bit integers".
SilentGhost
2009-12-11 11:49:44
for example, i have this in my server side codedata = conn.recv(1000000)as long as i understand i receive bytes... so i want data[0] to be treated as "unsigned 8 bit integer". how is this possible?
bbb
2009-12-11 11:59:17
This only works in Python 3.x. Python 2.6 has the b'string literal' syntax, but it is merely an alias for str, and older versions will give you a SyntaxError.
2009-12-11 12:14:18
@musicinmybrain: that's why this question is tagged as `python-3.x` I guess
SilentGhost
2009-12-11 12:21:01
+3
A:
Use the struct module.
import struct
value = struct.unpack('B', data[0])[0]
Note that unpack always returns a tuple, even if you're only unpacking one item.
Also, have a look at this SO question.
codeape
2009-12-11 11:49:51
data[0] is the first byte that you receive. unpack("B", data[0]) treats that byte as a 8-bit unsigned integer (known as unsigned char in C) and returns a tuple containing that integer (had you passed two bytes to unpack you would do something like unpack("BB", data[0:2]) and get a 2-tuple back). The final [0] gets the first (and only) item in the tuple.
codeape
2009-12-11 12:07:32
A:
Another very reasonable and simple option, if you just need the first byte’s integer value, would be something like the following:
value = ord(data[0])
If you want to unpack all of the elements of your received data at once (and they’re not just a homogeneous array), or if you are dealing with multibyte objects like 32-bit integers, then you’ll need to use something like the struct module.