How do you do binary addition on python?

[Fuugie]

I'm having trouble trying to add these together correctly. I have kind of ran into a brick wall. I have gotten it converted and that's it as of now.

My Code:

class BinaryNumber:
    '''A Binary Number Class'''
    #pass
    def __init__(self, bitString = ''):
        '''Constructor'''
        #pass
        self._bits = bitString

    def __str__(self):
        '''string representation'''
        if self._bits:
            return self._bits
        else:
            return '0'

    def __int__(self):
        '''conversion'''
        #pass
        total = 0
        for pos in range(len(self._bits)):
            if self._bits[pos] == '1':
                total += 2 ** (len(self._bits) - 1 - pos)
        return total

    def __add__(self, other):
        '''addition: implementation of the + operator'''
        pass

I am not allowed to import math either.

Any help would be much appreciated! :]

[bvdet]

All you need is a conversion of a decimal integer to binary. Then your magic method __add__ would be:

    def __add__(self, other):
        '''addition: implementation of the + operator'''
        return self.dec2bin((int(self)+int(other)))

Have you tried to write code for it?

[Fuugie]

I have tried a similar code that used "import math" and tried changing it to get it to work, but it didn't.

This is all of my code as of right now for my project:

# Program: ex6_18.py
# Authors: Robert Mineweaser
#
# This example is discussed in Chapter 6 of the book
# Object-Oriented Programming in Python
#

class BinaryNumber:
    '''A Binary Number Class'''
    #pass
    def __init__(self, bitString = ''):
        '''Constructor'''
        #pass
        self._bits = bitString

    def __str__(self):
        '''string representation'''
        if self._bits:
            return self._bits
        else:
            return '0'

    def __int__(self):
        '''conversion'''
        #pass
        total = 0
        for pos in range(len(self._bits)):
            if self._bits[pos] == '1':
                total += 2 ** (len(self._bits) - 1 - pos)
        return total

    def __add__(self, other):
        '''addition: implementation of the + operator'''
        #pass
        '''carry = 0
        result = ''
 
        # Work from right to left.
        for i in range(0, len(self._bits))[::-1]:
            tmp = int(((a[i]) + int(b[i]) + carry)/2)
            res = str(int(a[i]) + int(b[i]) + carry - 2 * tmp)
            result += res
            carry = tmp
 
        result = (result + str(carry))[::-1]
        try:
            return result[result.index('1'):]
        except ValueError, ex:
            return '0'
              '''
        return self.dec2bin((int(self)+int(other)))
    
    def __subtract__(self, other):
        '''subtraction: implementation of the - operator'''     # Optional
        pass

    def __lt__(self, other):
        '''less: implementation of the < operator'''
        #pass
        if int(a) <= int(b):
            return True
        else:
            return False
    
    def __gt__(self, other):
        '''great: implementation of the > operator'''
        #pass
        if int(a) >= int(b):
            return True
        else:
            return False

    def __eq__(self, other):
        '''equal: implementation of the = operator'''
        #pass
        if int(a) == int(b):
            return True
        else:
            return False


if __name__ == '__main__':
    a  = BinaryNumber('01111001')   # binary numbers must start with 0
    b  = BinaryNumber('00110101')   # a = 121, b = 53
    print 'a = ', a, int(a)
    print 'b = ', b, int(b)

    print 'a + b', a + b, int(a + b)
    #print 'a - b', a - b, int(a - b)    # optional

    print 'a < b', a < b
    print 'a > b', a > b
    print 'a == b', a == b

print 'Press the Enter key to finish'

raw_input()

If you couldn't tell, subtraction is optional and I commented the code i tried to change to get to work. Any advice on what I could do to fix this.

[bvdet]

Function dec2bin() would be a class method. Check out this thread.

[Fuugie]

Alright. After it is added together, I need my output to show as " a + b (binary result) (decimal result). How would I make it add them together and have it show that as the result of the two?

[bvdet]

Modify the string returned by __add__ and use string formatting. Untested:

return "%s + %s (%s) (%s)" % (self, other, self.dec2bin((int(self)+int(other))), (int(self)+int(other)))

[Fuugie]

I am still a little confused. All I need to do is add 2 binary numbers together and have the output be " a + b (binary result) (decimal result) ". The conversion was to just give me the decimal result. So how would I go about adding this all together to get the given output, " a + b (binary result) (decimal result) " ? If you don't understand what I am trying to ask please feel free to tell me.

This was my original code for " __add__" without any additions from me:

class BinaryNumber:
    '''A Binary Number Class'''
    #pass
    def __init__(self, bitString = ''):
        '''Constructor'''
        #pass
        self._bits = bitString

    def __str__(self):
        '''string representation'''
        if self._bits:
            return self._bits
        else:
            return '0'

    def __int__(self):
        '''conversion'''
        #pass
        total = 0
        for pos in range(len(self._bits)):
            if self._bits[pos] == '1':
                total += 2 ** (len(self._bits) - 1 - pos)
        return total

    def __add__(self, other):
        '''addition: implementation of the + operator'''
        pass
            
    def __subtract__(self, other):
        '''subtraction: implementation of the - operator'''     # Optional
        pass

    def __lt__(self, other):
        '''less: implementation of the < operator'''
        #pass
        if int(a) <= int(b):
            return True
        else:
            return False
    
    def __gt__(self, other):
        '''great: implementation of the > operator'''
        #pass
        if int(a) >= int(b):
            return True
        else:
            return False

    def __eq__(self, other):
        '''equal: implementation of the = operator'''
        #pass
        if int(a) == int(b):
            return True
        else:
            return False

if __name__ == '__main__':
    a  = BinaryNumber('01111001')   # binary numbers must start with 0
    b  = BinaryNumber('00110101')   # a = 121, b = 53
    print 'a = ', a, int(a)
    print 'b = ', b, int(b)

    print 'a + b', a + b, int(a + b)
    #print 'a - b', a - b, int(a - b)    # optional

    print 'a < b', a < b
    print 'a > b', a > b
    print 'a == b', a == b

print 'Press the Enter key to finish'

raw_input()

[bvdet]

See my first post in this thread.

[Fuugie]

Yes, but even when I put that in, I get an error, "AttributeError : BinaryNumber instance has no attribute 'dec2bin'". How exactly would I have to make this code to look to get it to add the binary numbers together correctly and have it give me the output, "a + b (binary result) (decimal result)" ?

[bvdet]

You must add a BinaryNumber method dec2bin(). The method must return the decimal number converted to binary.

[Fuugie]

Is this the only way to do it? Or is there another way possible? If not, how would I go about doing this?

[bvdet]

That is the way I would do it, because that's the easiest for me. There are other ways though. You can write the code to do binary addition and subtraction in methods __add__() and __sub__() respectively. Check out this website.

[Fuugie]

I understand the concepts of binary addition, but I just have trouble putting it into code. How would I write the code for binary addition in the method __add__?

[bvdet]

I am sorry, but I cannot write the code for you. Please show some effort on your own, then we can help. Since you understand the concepts of binary addition, you may know more than me about it.

Even if you do the binary addition, I think the code should go into a separate function.

[Glenton]

Hi

It seems to me that, since you're implementing your own version of this, you might as well do the addition in binary. Your bitString is just a string of 1s and 0s, if I'm not mistaken?

So, I would first implement something that returns a single digit in a given position.

Something like:

def binDigit[self,position]:
    if position>len(self._bits):
        return 0
    else:
        return self._bits[-position]

if self._bits="101 ", then position[1] = 1, position[2]=0, position[3]=1 and position[4]=0 etc.

Now create something that does the addition bit by bit (literally!):

def __add__[self,other]:
    v=max([len(self._bits),len(other._bits)])+1
    ans=''
    carry=0
    for i in range(1,v+1):
        a=self.position(i)
        b=self.position(i)
        t=carry+int(a)+int(b)        
        if t<=1:
            carry=0
        else:
            carry=1        
        if t%2==0:
            ans='0'+ans
        else:
            ans='1'+ans
    return BinaryNumber(ans)

I haven't checked any of this, but it should give you some idea.