How to write individual bits to a text file in python?

Question

Suppose I have a number like 824 and I write it to a text file using python. In the text file, it will take 3 bytes space. However, If i represent it using bits, it has the

Answer 1

The struct module is what you want. From your example, 824 = 0000001100111000 binary or 0338 hexadecimal. This is the two bytes 03H and 38H. struct.pack will convert 824 to a string of these two bytes, but you also have to decide little-endian (write the 38H first) or big-endian (write the 03H first).

Example

>>> import struct
>>> struct.pack('>H',824) # big-endian
'\x038'
>>> struct.pack('>> struct.pack('H',824)  # Use system default
'8\x03'

struct returns a two-byte string. the '\x##' notation means (a byte with hexadecimal value ##). the '8' is an ASCII '8' (value 38H). Python byte strings use ASCII for printable characters, and \x## notation for unprintable characters.

Below is an example writing and reading binary data to a file. You should always specify the endian-ness when writing to and reading from a binary file, in case it is read on a system with a different endian default:

import struct

a = 824
bin_data = struct.pack('

Output

bin_data length: 2
Value from file: 824
bin_data representation: '8\x03'
Byte 0 as binary: 00111000
Byte 1 as binary: 00000011