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: float) -> str:
    """
    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 isinstance(decimal, (int, float))
    assert decimal == int(decimal)
    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()