Hexadecimal Conversion: Solution

def hex_convert(hex_in):
    """Convert a hexadecimal string, like '1A', into it's decimal equivalent."""

    # START SOLUTION

    # Dictionary to convert a hex character to equivalent decimal value

    CONVERT = {
        '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
    }

    # Straightforward solution: for each digit, multiply it's value
    # by 16 ** (position):

    result = 0
    for i, hex_char in enumerate(hex_in):
        hex_digit = CONVERT[hex_char]
        power = 16 ** (len(hex_in) - i - 1)
        result = result + hex_digit * power

    return result