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Binary to decimal and vice-versa in python

  • Difficulty Level : Easy
  • Last Updated : 29 Jun, 2021

Write Python code for converting a decimal number to it’s binary equivalent and vice-versa.

Example: 

From decimal to binary
Input : 8
Output : 1 0 0 0

From binary to decimal
Input : 100
Output : 4

Decimal to binary  

Keep calling conversion function with n/2  till n > 1,
later perform n % 1 to get MSB of converted binary number.  
Example :- 7
1). 7/2 = Quotient = 3(greater than 1), Remainder = 1.
2). 3/2 = Quotient = 1(not greater than 1), Remainder = 1.
3). 1%2 = Remainder = 1.
Therefore, answer is 111.

Python3




# Function to print binary number for the
# input decimal using recursion
def decimalToBinary(n):
 
    if(n > 1):
        # divide with integral result
        # (discard remainder)
        decimalToBinary(n//2)
 
     
    print(n%2, end=' ')
     
     
 
# Driver code
if __name__ == '__main__':
    decimalToBinary(8)
    print("\n")
    decimalToBinary(18)
    print("\n")
    decimalToBinary(7)
    print("\n")

Output: 

1 0 0 0 
1 0 0 1 0 
1 1 1 

Decimal to binary using bin(): 



Python3




# Function to convert Decimal number
# to Binary number
 
def decimalToBinary(n):
    return bin(n).replace("0b","")
 
# Driver code
if __name__ == '__main__':
    print(decimalToBinary(8))
    print(decimalToBinary(18))
    print(decimalToBinary(7))

Output: 

1000
10010
111

Binary to decimal 

Example -: 1011
1). Take modulo of given binary number with 10. 
    (1011 % 10 = 1)
2). Multiply rem with 2 raised to the power
    it's position from right end. 
    (1 * 2^0)
    Note that we start counting position with 0. 
3). Add result with previously generated result.
    decimal = decimal + (1 * 2^0)
4). Update binary number by dividing it by 10.
    (1011 / 10 = 101)
5). Keep repeating upper steps till binary > 0.

Final Conversion -: (1 * 2^3) + (0 * 2^2) +
                 (1 * 2^1) + (1 * 2^0) = 11

Python3




# Function calculates the decimal equivalent
# to given binary number
 
def binaryToDecimal(binary):
     
    binary1 = binary
    decimal, i, n = 0, 0, 0
    while(binary != 0):
        dec = binary % 10
        decimal = decimal + dec * pow(2, i)
        binary = binary//10
        i += 1
    print(decimal)   
     
 
# Driver code
if __name__ == '__main__':
    binaryToDecimal(100)
    binaryToDecimal(101)
    binaryToDecimal(1001)

Output: 

4
5
9

Binary to decimal using int(): 

Python3




# Function to convert Binary number
# to Decimal number
 
def binaryToDecimal(n):
    return int(n,2)
 
 
# Driver code
if __name__ == '__main__':
    print(binaryToDecimal('100'))
    print(binaryToDecimal('101'))
    print(binaryToDecimal('1001'))

Output: 

4
5
9

This article is contributed by Pushpanjali Chauhan. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 

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