Bit by Bit manipulation in python

Question

I'm currently writing a program in python that compresses a file using Huffman coding. Because of python I have been having problems trying to program on such a low level. A problem that I was not able to wrap my head around is decoding (I encode the file I'm reading in a .bin file), because everything I have found so far reads the binary file byte by byte or as hex, I am not able to implement decompression.

So my question is, can I read a binary file in python bit by bit such as to have a variable: binary_text = '0b1000101000...'

Does this answer your question? How to read bits from a file? — Tomerikoo
– Tomerikoo, Commented Jan 1, 2021 at 21:36

alex_noname · Accepted Answer · 2021-01-02 10:53:20Z

2

You also could use bitstream library. It allows to represent bytes as a binary stream:

>>> from bitstream import BitStream
>>> BitStream(b"Hello World!")
010010000110010101101100011011000110111100100000010101110110111101110010011011000110010000100001

You can read and write bits by means of read and write functions, like so:


>>> stream = BitStream()        # <empty>
>>> stream.write(True, bool)    # 1
>>> stream.write(False, bool)   # 10
>>> stream.read(bool, 2)        # <empty>
[True, False]

The documentation and more examples you can find here.

Update:

Another good alternative is bitarray library, implemented in C and providing rich functionality for manipulating bit streams.

edited Jan 2, 2021 at 10:53

answered Jan 1, 2021 at 21:11

alex_noname

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Comments

Kyle Silver · Accepted Answer · 2021-01-01 20:38:29Z

0

You should just be able to open the file in rb (read binary) mode and then use .read on the file handle. Here’s the relevant docs for python’s read: https://docs.python.org/3/library/functions.html#open

with open('my_file.txt', 'rb') as f:
    eight_bytes = f.read(8)

>>> print(eight_bytes)
b'hello wo'
>>> eight_bytes[0]
104

answered Jan 1, 2021 at 20:38

Kyle Silver

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Comments

Mark Adler · Accepted Answer · 2021-01-01 23:01:42Z

0

Don't know why the "0b" would be useful, but anyway:

import numpy as np
bin = np.fromfile("file.bin", 'u1')
binary_text = "0b"
for byte in bin:
    for mask in [128, 64, 32, 16, 8, 4, 2, 1]:
        binary_text += '1' if byte & mask else '0'
print(binary_text)

edited Jan 1, 2021 at 23:01

answered Jan 1, 2021 at 21:43

Mark Adler

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