Converting Integer to Binary in Python

Converting integer to binary in python

>>> '{0:08b}'.format(6)
'00000110'

Just to explain the parts of the formatting string:

• {} places a variable into a string
• 0 takes the variable at argument position 0
• : adds formatting options for this variable (otherwise it would represent decimal 6)
• 08 formats the number to eight digits zero-padded on the left
• b converts the number to its binary representation

If you're using a version of Python 3.6 or above, you can also use f-strings:

>>> f'{6:08b}'
'00000110'

Python int to binary string?

Python's string format method can take a format spec.

>>> "{0:b}".format(37)
'100101'

Format spec docs for Python 2

Format spec docs for Python 3

Convert base-2 binary number string to int

You use the built-in int() function, and pass it the base of the input number, i.e. 2 for a binary number:

>>> int('11111111', 2)
255

Here is documentation for Python 2, and for Python 3.

Converting a calculated decimal number into 8 bit binary

You do have to print the value:

>>> print(bin(160))  # This version gives the 0b prefix for binary numbers.
0b10100000
>>> print(format(160,'08b'))  # This specifies leading 0, 8 digits, binary.
10100000
>>> print('{:08b}'.format(160)) # Another way to format.
10100000
>>> print(f'{160:08b}')  # Python 3.6+ new f-string format.
10100000

Converting a number to binary with a variable length

You can nest {} formats in f-strings:

>>> s = 6
>>> l = 7
>>> a = f'{s:0{l}b}'
>>> print(a)
0000110

Converting an Integer to Binary in Python

• Removed recursion.
• Condition should be num != 0.
• Use divmod built-in function for getting both quotient and remainder.
• Removed redundant modnum checks.

Assuming these issues we can write

def func(num):
    if num == 0:
        return [num]

    binary_digits = []    
    while num != 0:
        num, modnum = divmod(num, 2)
        binary_digits.append(modnum)
    return list(reversed(binary_digits))

num = int(input("Enter the Number"))
binary_digits = func(num)
print(binary_digits)

Example:

>>> func(100)
[1, 1, 0, 0, 1, 0, 0]

Convert integer to binary and then do a left bit shift in python

You can do the bit shift before converting to binary, since the bit shifting doesn't care about the base of your integer (bit shifting is by definition done in the base of 2).

i = 6 << 12
answer = bin(i)[2:]

Edit: Alternative binary conversion from @guidot

i = 6 << 12
answer = "{:b}".format(i)

Additional conversions

Just for the fun of it, here's some other ways to bit shift a number:

i = 6 * (2**12) # This will convert into 6 * 2^12
answer = "{:b}".format(i)

A bit shift will double the numbers value, so by multiplying the bitshift with the power two we achieve the same thing:

> print(6 << 12)
24576
> print(6 * 2**12)
24576

It's generally better to use bit shift if you know you only want to double the value.

You can also convert it to binary and then add 13 trailing zeroes, a funky way to achieve the same functionality:

i = 6 # Notice: No operation here this time
answer = "{:b}".format(i) + ('0' * 12)

Maybe not recommended to use the last method, but it illustrates how (left) bit shifting works.

Converting Integer to Binary Using the Math Module (Python)

Since you say that you are trying to convert the integer 'manually' to binary, I am assuming that you are not willing to use the bin() function. Here is something you can try.

from math import*
x= int(raw_input('Enter the decimal number'))
n=[]
while x>1:
    y=int(x%2)
    n=n+[y]
    x=floor(x/2.0)
if x==1:
    n=n+[1]
elif x==0:
    n=n+[0]
size=len(n)
print 'binary equivalent =',
y=-1
while y>=-size:
    print n[y],
    y=y-1
print ''

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