Workin with binary in python

Question

Is there an easy way to work in binary with Python?

I have a file of data I am receiving (in 1's and 0's) and would like to scan through it and look for certain patterns in binary. It has to be in binary because due to my system, I might be off by 1 bit or so which would throw everything off when converting to hex or ascii.

For example, I would like to open the file, then search for '0001101010111100110' or some string of binary and have it tell me whether or not it exists in the file, where it is, etc.

Is this doable or would I be better off working with another language?

If you don't mind expanding your data by 8x or so you could convert it to a string, then use the usual string search facilities. — Mark Ransom
– Mark Ransom, Commented Apr 17, 2013 at 22:28

Mark Ransom · Accepted Answer · 2013-04-18 00:24:06Z

4

To convert a byte string into a string of '0' and '1', you can use this one-liner:

bin_str = ''.join(bin(0x100 + ord(b))[-8:] for b in byte_str)

Combine that with opening and reading the file:

with open(filename, 'rb') as f:
    byte_str = f.read()

Now it's just a simple string search:

if '0001101010111100110' in bin_str:

edited Apr 18, 2013 at 0:24

answered Apr 17, 2013 at 22:32

Mark Ransom

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4 Comments

DSM Over a year ago

I think something like ''.join('{:08b}'.format(ord(b)) for b in byte_str) looks a little cleaner.

Mark Ransom Over a year ago

@DSM, you might be right. I just went with the first thing I thought of.

tdfoster Over a year ago

This works well. Just out of curiosity, in the first code what is the purpose of the 0x100? is that a mask? or the 08b in the second? I expect my file to be ~10-1000kB so could this throw off importing the entire file?

Mark Ransom Over a year ago

@tdfoster, it turns out bin doesn't give you leading zeros so I had to add 0x100 to make sure they were there. That leading 1 and the 0b before it get stripped off with the [-8:]. DSM's suggestion should result in the same string.

James · Accepted Answer · 2013-04-17 22:31:22Z

0

You would be better working off another language. Python could do it (if you use for example, file = open("file", "wb")

(appending the b opens it in binary), and then using a simple search, but to be honest, it is much easier and faster to do it in a lower-level language such as C.

answered Apr 17, 2013 at 22:31

James

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3 Comments

DSM Over a year ago

I'm not so sure of that. Could you give an example implementation in C to compare with the four-line Python version above?

tdfoster Over a year ago

I am using SWIG and a good ammount of C so I think I will give both options a try. Thanks!

James Over a year ago

python is simpler, but I meant that C would be faster.

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