How to get binary representation of negative numbers in python

Question

When I enter bin(-3) it just shows -0b11.

Which is not what I want. It just keeps that - sign and convert the number. I want the actual representation of negative numbers.

Is there any method in python which does that?

@jonrsharpe Yeah two complement representation. Upto, standard 32 bit. — Bhavesh Munot, Feb 07 '15 at 15:01

falsetru · Answer 1 · 2015-02-07T15:13:26.823

26

Depending on how many binary digit you want, subtract from a number (2ⁿ):

>>> bin((1 << 8) - 1)
'0b11111111'
>>> bin((1 << 16) - 1)
'0b1111111111111111'
>>> bin((1 << 32) - 1)
'0b11111111111111111111111111111111'

UPDATE

Using following expression, you can cover both positive and negative case:

>>> bin(((1 << 32) - 1) & -5)
'0b11111111111111111111111111111011'

edited Feb 07 '15 at 15:13

answered Feb 07 '15 at 15:01

falsetru

And even `>>> bin((1 << 64) - 1) '0b1111111111111111111111111111111111111111111111111111111111111111'` – ForceBru Feb 07 '15 at 15:03
7

For bonus points, you can cover positive and negative in one go with bitwise and: `bin(((1 << 32) - 1) & -5)` – cobbal Feb 07 '15 at 15:10
@cobbal, Thank you for your comment. I updated the answer according to you. – falsetru Feb 07 '15 at 15:13

1 Answers1