Question

[Using Python]

Write a program to convert a hexadecimal number to its decimal value.

(Reminder: hexadecimal numbers are 0 through 9, A,B,C,D,E,F. hex(A) = 10, hex(F) = 15).

example outputs:

1. `Enter a hex number: f`

`The decimal value for hex number f is 15`

2. `Enter a hex number: g`

`Incorrect hex number`

3. `Enter a hex number: 091c`

`The decimal value for hex number 091c is 2332`

4. `Enter a hex number: 091g`

`Incorrect hex number`

Hints:

• you need to use the ord builtin function
• you need to iterate through the input hex number using a loop, referencing the index of each hex character
• you need to convert the input hex number to upper case
• Make sure there is a invalid response for invalid input.

Answer 1

# function to convert the hexadecimal number to its decimal equivalent

def hex_to_decimal(hex_num):

    # dictonary to tell the value of hex num

    hex = {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9, 'A': 10, 'B': 11, 'C': 12, 'D': 13, 'E': 14, 'F': 15}

    # creating list of chars and reversing it

    hex_num = hex_num.upper()

    chars = list(hex_num)

    chars.reverse()

    decimal = 0

    # looping through each char and adding to result

    for i in range(len(chars)):

        # if invalid input

        if chars[i] not in hex:

            return -1

        else:

            decimal += hex[chars[i]] * (16 ** i)

            print()

    

    # return the decimal value

    return decimal

# driver code

if __name__ == "__main__":

    hex_num = input('Enter a hex number: ')

    if hex_to_decimal(hex_num) == -1:

        print('Incorrect hex number')

    else:

        print('The decimal value for hex number {} is {}'.format(hex_num, hex_to_decimal(hex_num)))

Enter a hex number: f The decimal value for hex number f is 15

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