How to shift bits in a 2-5 byte long bytes object in python?

binary-data, bit-shift, python, python-3.x

Solution

Don't use `bytes` to represent integer values; if you need bits, convert to an `int`:

value = int.from_bytes(your_bytes_value, byteorder='big')
bits_21_to_8 = (value & 0x1fffff) >> 8

where the `0x1fffff` mask could also be calculated with:

mask = 2 ** 21 - 1

Demo:

>>> your_bytes_value = b'\x93\x4c\x00'
>>> value = int.from_bytes(your_bytes_value, byteorder='big')
>>> (value & 0x1fffff) >> 8
4940

You can then move back to bytes with the `int.to_bytes()` method:

>>> ((value & 0x1fffff) >> 8).to_bytes(2, byteorder='big')
b'\x13L'

Problem

I am trying to extract data out of a byte object. For example: From `b'\x93\x4c\x00'` my integer hides from bit 8 to 21. I tried to do `bytes >> 3` but that isn't possible with more than one byte. I also tried to solve this with struct but the byte object must have a specific length. How can I shift the bits to the right?

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