How to Read Bytes from a file

[Bart Ogryczak]

On Mar 1, 7:52 am, "gregpin... at gmail.com" <gregpin... at gmail.com>
wrote:
> It seems like this would be easy but I'm drawing a blank.
>
> What I want to do is be able to open any file in binary mode, and read
> in one byte (8 bits) at a time and then count the number of 1 bits in
> that byte.
>
> I got as far as this but it is giving me strings and I'm not sure how
> to accurately get to the byte/bit level.
>
> f1=file('somefile','rb')
> while 1:
>     abyte=f1.read(1)

import struct
buf = open('somefile','rb').read()
count1 = lambda x: (x&1)+(x&2>0)+(x&4>0)+(x&8>0)+(x&16>0)+(x&32>0)+
(x&64>0)+(x&128>0)
byteOnes = map(count1,struct.unpack('B'*len(buf),buf))

byteOnes[n] is number is number of ones in byte n.