Create a file from its binary value in python

Question

I've created a script which allows me to read the binary representation of a whole file, yet I couldn't find a way to write the binary stream back to a file using python.

The code I'm using to get the binary value is the following:

 fileBin = ""
 bytes = bytearray(open(file, "rb").read())
 for i in range(0, len(bytes)):
     fileBin = fileBin + str(('{:08b}'.format(bytes[i])))
 return fileBin

If I understood correctly you want to convert binary file to a file full of 0s and 1s. You could just open file normally and write it as a string. — matejm, May 01 '17 at 15:36
@matejm maybe I wrote the post in a confused way: Given a binary string representing an entire file, I want to re-create the read file. — dec0de_d00dle, May 01 '17 at 15:40
So you want just convert every 8 characters back to `byte` object? — matejm, May 01 '17 at 15:52
No, I tried with byte and bytearray yet I have to find a way to create the file from the stream and not just write into a new file. — dec0de_d00dle, May 01 '17 at 15:55
Looks like this is more of a copy operation, answered [here|http://stackoverflow.com/questions/16630789/python-writing-binary-files-bytes] — ciacicode, May 01 '17 at 18:13
@ciacicode Actually I have to work on single bytes, I need to open the file work on it and create a new one from a string made of binary code only. — dec0de_d00dle, May 01 '17 at 19:21
@ciacicode I think I omitted a fundamental detail: I'm working with steganography hence I need to re-create a file using only the last bit of every byte of the "host file", not the whole byte. — dec0de_d00dle, May 02 '17 at 15:07
Thing is that in your example I cannot see any instance where you: a) create a file ` with open ('file', 'wb') as f: ` and b) when you write those bytes in it with a` f.write(bytes)` In the example you return the bytes but don't really write them anywhere. — ciacicode, May 03 '17 at 11:47

score 0 · Accepted Answer · answered May 05 '17 at 16:26

I was able to find a solution and to write a whole new file using bytes. The problem is all about the code used to represent the string: while trying to write a bit string (i.e. "101010111000") I was actually writing its ASCII value in a text file.

what you need to do it:

take every 8 characters of the string
convert those characters in int
cast the result to end up with bytes (I casted a whole list)
profit

The code I used is the following:

    """Reads file as binary string"""
    def openFileBinary(file):
         fileBin = ""
         bytes = bytearray(open(file, "rb").read())
         for i in bytes:
             fileBin = fileBin + str(('{:08b}'.format(i)))
         return fileBin

    """Writes string to file as binary"""
    def writeFile(stream):
        with open("output", "wb") as f:
          f.write(bitstring_to_bytes(stream))

    """Converts binary string into bytes"""
    def bitstring_to_bytes(s):
        b = bytearray()
        w = [int(s[i:i+8],2) for i in range(0, len(s), 8)]
        return(bytes(w))

It was a terrible solution to use strings! I've continued working on the project and rewrote the code to work with bytearrays only! — dec0de_d00dle, Jul 15 '17 at 20:25

Create a file from its binary value in python

1 Answers1