make binary number its 'opposite' in python

Question

trying to take a list of binary numbers, and display their 'opposites', im putting this word in quotes because I'm not sure if it's the best way to describe what I mean.

board=[1,10,101]

I want to make a function that will show the complement of opposite of these numbers like this:

newboard=[0,01,010]

basically swapping the 0 for a 1 and the 1 for a 0. Since they are integers I cant iterate through each binary number and manually change the value, I've tried using two's compliment but that doesn't semantically do what I'm trying to do it seems. Does anyone know a function for how to do this, or what this process would be called? thanks!

You can't create a `01` integer either (that'd just be `1`). It looks ilke strings containing `1` and `0` characters would be a a better fit (at which point swapping characters is easy enough). — Martijn Pieters, Feb 06 '17 at 22:35
Like `0b101 ^ 0b111 == 0b010`? But note that you'll see the decimal representation - `5 ^ 7 == 2`. You don't have `0b101` in your list, you have `101`. — jonrsharpe, Feb 06 '17 at 22:37

score 1 · Answer 1 · answered Feb 06 '17 at 23:12

1

Can you represent your binary numbers as strings? Then you could simply do the following:

opposite = { '0':'1', '1':'0'}
board=['1', '10', '101']
newboard = [''.join([opposite[c] for c in n]) for n in board]

answered Feb 06 '17 at 23:12

fjarino

191
4

score 0 · Answer 2 · answered Feb 06 '17 at 23:14

You can't really store [0, 01, 010] in a list as it just becomes [0, 1, 10] you can use strings though

def reverse_binary(input):
    reversed = []
    for x in [list(str(x)) for x in input]:
        reversed.append(''.join(['%s' % (int(x) ^ 1) for x in x]))
    return reversed


if __name__ == '__main__':
    print(reverse_binary([1, 10, 101]))

Wso · Answer 3 · 2017-02-07T00:57:47.047

You can swap all the ones for zeros and all the zeros for ones inside every string. To do this simple iterate over the list, and for each value, create a new entry swapping 1 and 0. In order to preform the swap, replace '1' with a value thats never used (such as 'U'), assign '0' to '1' and assign the temp value 'U' to '0'.

newboard = [a.replace('1','U').replace('0','1').replace('U','0') for a in board]

score 0 · Answer 4 · edited May 23 '17 at 12:01

I believe what you are referring to is just called complementing numbers; you are trying to flipping the digits of binary numbers. The natural thing to do is to use the XOR operator. Consider the following piece of code:

get_bin = lambda x: format(x, 'b')
def Complement_binary(x):
    complemented = []
    for num in x:
        i = 1
        while i <= num:
            i = i << 1
        complemented.append(get_bin((i - 1) ^ num))
    return complemented

The Complement_binary function receives a list of numbers and returns a list of numbers in binary representation in strings (get_bin converts the numbers to binary numbers in strings). If you don't want strings, you may remove the get_bin function in complemented.append(get_bin((i - 1) ^ num)).

Source for get_bin function: https://stackoverflow.com/a/21732313/6833761 by @Martin Thoma

make binary number its 'opposite' in python

4 Answers4