# Python Decimal to Binary converter (without using bin() or output formatting)

There is no input validation for this, but that aside, I would appreciate it if anyone could help me improve the logic of this script.

import math
#Input
num = input("Enter a whole number: ")

#Floors input in case of a non whole number
decimal = math.floor(float(num))

#Variables
exp = 0
divTwo = 1
zeros = 0
total = ""
if decimal < 0:
total += str('-')
decimal = -decimal
if decimal == 0:
total = str('0')
else:
#Loops while remainder is > 0.
while int(decimal) > 0:

#Increases exponent by one if 2^exp is less than or equal to the remainder.
if 2 ** exp <= int(decimal):
exp += 1

else: #Multiplies 2 by the exponent and places zeros in between 1s. Also subtracts from the exponent.
exp -= 1

#Determines whether or not to subtract from the remainder and add a '1' to the binary translation or just add a '0' to the binary translation.
if 2 ** exp <= int(decimal):

#Counts how many zeros need to be added to the end of the binary translation.
if 2 ** exp == int(decimal):
divTwo = int(decimal)

#Loops until all remaining zeros have been accounted for.
while divTwo > 1:
divTwo = divTwo / 2
zeros += 1

decimal = int(decimal)
decimal -= 2 ** exp
total += str('1')

else:
total += str('0')

#Places remaining zeros.
while zeros > 0:
total += str('0')
zeros -= 1

print ('Binary: ' + total)
input()

#
#
#Or 'bin(decimal)' works too, but this was for fun
#
#


Here is a working version of the script.

• Just to be sure. You know you can do "{0:b}".format(num) right? Jun 30, 2016 at 21:23
• I haven't looked into formatting that much. Jun 30, 2016 at 21:27
• What about bin(x)[2:] then? Jun 30, 2016 at 21:32
• I did this with the intention of not using bin() Jun 30, 2016 at 21:36

• You can remove half of you code.
You need the variables exp, total and decimal. The rest are just noise.

• You should remove all the int(decimal)s, decimal is only ever subtracted from, and so it's not going to become a float. And so these are not needed.

1. You can remove all the code in if 2 ** exp == int(decimal):, instead just use exp as you do zeros.

2. You should split your while loop so that it only does one thing at a time. You want an int log and then a while loop that converts the input to binary.

3. You can replace while zeros > 0: with Pythons way to duplicate strings. 0 * zeros.

4. You should make this a function.

def binary(number): # 4
output = ''
if number < 0:
output = '-'
number = -number

exp = 1
while 2 ** exp <= number: # 2
exp += 1

while number > 0:
exp -= 1
if 2 ** exp <= number:
number -= 2 ** exp
output += '1'
else:
output += '0'

return output + '0' * exp # 1, 3

number = int(input("Enter a whole number: "))
print('Binary: ' + binary(number))

• It works for the most part, however it freezes if you input 2. Everything above 2 works. Even 1 works. Jul 1, 2016 at 14:18
• @Confettimaker That's correct, I mistakenly at some point removed the = from 2 ** exp <= number. Jul 1, 2016 at 14:31