Inverting bits in python

Question

I am doing some calculations and I was wondering how you can invert a byte in python.

For example:

0b11111111 should be flipped to 0b00000000.

I have tried turning into a string and flipping it then but I cant somehow turn it back into a Integer.

Also, I want to add that the ~ does not work, as it simply just makes the same number but negative

@trincot already tried that. It Simply shows as syntax error. — plras45151152135, Jun 22 '21 at 10:22
Does this answer your question? [How do I do a bitwise Not operation in Python?](https://stackoverflow.com/questions/31151107/how-do-i-do-a-bitwise-not-operation-in-python) — Rares Dima, Jun 22 '21 at 10:23
Syntax error? Did you look at the documentation? for instance: `0b10101 ^ 0b11111111 == 0b11101010` — trincot, Jun 22 '21 at 10:28
@trincot Okay I got! `a = 0b11111111^0b00101010 print(bin(a))` This gives me The opposite — plras45151152135, Jun 22 '21 at 10:30

Андрей Беспалов · Accepted Answer · 2021-06-22T10:32:41.220

1

 bin(0b11010111 ^ 0b11111111) // bit subtraction
 # Result
 # bin(0b11010111 ^ 0b11111111)
 #'0b101000'
 # for each bit subtraction with 1 occur

edited Jun 22 '21 at 10:32

answered Jun 22 '21 at 10:29

Андрей Беспалов

160
7

Could you add an explanation of your solution? – Klaus D. Jun 22 '21 at 10:31
I added comments to solution – Андрей Беспалов Jun 22 '21 at 10:33

score 1 · Answer 2 · answered Jun 22 '21 at 11:37

To explain why ~ "dit not work": you want to invert all bits in a byte (8-bits), but the 0b.... value is not a byte, but an int which has more bits than just 8. ~var inverts all bits in an integer. You can clear all bits except the lowest 8 with a mask to get the result you expect:

MASK8 = 0b11111111  # or 255 decimal

v = 0b11101110                                                                                                                                                    
inv = ~v & MASK8    # 0b10001

Inverting bits in python

2 Answers2