Python/conversions/decimal_to_hexadecimal.py

""" Convert Base 10 (Decimal) Values to Hexadecimal Representations """

# set decimal value for each hexadecimal digit
values = {
    0: "0",
    1: "1",
    2: "2",
    3: "3",
    4: "4",
    5: "5",
    6: "6",
    7: "7",
    8: "8",
    9: "9",
    10: "a",
    11: "b",
    12: "c",
    13: "d",
    14: "e",
    15: "f",
}


def decimal_to_hexadecimal(decimal):
    """
        take integer decimal value, return hexadecimal representation as str beginning
        with 0x
        >>> decimal_to_hexadecimal(5)
        '0x5'
        >>> decimal_to_hexadecimal(15)
        '0xf'
        >>> decimal_to_hexadecimal(37)
        '0x25'
        >>> decimal_to_hexadecimal(255)
        '0xff'
        >>> decimal_to_hexadecimal(4096)
        '0x1000'
        >>> decimal_to_hexadecimal(999098)
        '0xf3eba'
        >>> # negatives work too
        >>> decimal_to_hexadecimal(-256)
        '-0x100'
        >>> # floats are acceptable if equivalent to an int
        >>> decimal_to_hexadecimal(17.0)
        '0x11'
        >>> # other floats will error
        >>> decimal_to_hexadecimal(16.16) # doctest: +ELLIPSIS
        Traceback (most recent call last):
        ...
        AssertionError
        >>> # strings will error as well
        >>> decimal_to_hexadecimal('0xfffff') # doctest: +ELLIPSIS
        Traceback (most recent call last):
        ...
        AssertionError
        >>> # results are the same when compared to Python's default hex function
        >>> decimal_to_hexadecimal(-256) == hex(-256)
        True
    """
    assert type(decimal) in (int, float) and decimal == int(decimal)
    hexadecimal = ""
    negative = False
    if decimal < 0:
        negative = True
        decimal *= -1
    while decimal > 0:
        decimal, remainder = divmod(decimal, 16)
        hexadecimal = values[remainder] + hexadecimal
    hexadecimal = "0x" + hexadecimal
    if negative:
        hexadecimal = "-" + hexadecimal
    return hexadecimal


if __name__ == "__main__":
    import doctest

    doctest.testmod()