Binary to decimal and vice-versa in python - GeeksforGeeks

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 recursiondef decimalToBinary(n):     if(n > 1):        # divide with integral result        # (discard remainder)        decimalToBinary(n//2)          print(n%2, end=' ')           # Driver codeif __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 codeif __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 codeif __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 codeif __name__ == '__main__':    print(binaryToDecimal('100'))    print(binaryToDecimal('101'))    print(binaryToDecimal('1001'))
Output: 
4
5
9
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