Python decimal 模块，ROUND_HALF_DOWN 实例源码

def __init__(self, min_value=None, max_value=None, force_string=False,
                 precision=2, rounding=decimal.ROUND_HALF_UP, **kwargs):
        """
        :param min_value: Validation rule for the minimum acceptable value.
        :param max_value: Validation rule for the maximum acceptable value.
        :param force_string: Store as a string.
        :param precision: Number of decimal places to store.
        :param rounding: The rounding rule from the python decimal library:

            - decimal.ROUND_CEILING (towards Infinity)
            - decimal.ROUND_DOWN (towards zero)
            - decimal.ROUND_FLOOR (towards -Infinity)
            - decimal.ROUND_HALF_DOWN (to nearest with ties going towards zero)
            - decimal.ROUND_HALF_EVEN (to nearest with ties going to nearest even integer)
            - decimal.ROUND_HALF_UP (to nearest with ties going away from zero)
            - decimal.ROUND_UP (away from zero)
            - decimal.ROUND_05UP (away from zero if last digit after rounding towards zero would have been 0 or 5; otherwise towards zero)

            Defaults to: ``decimal.ROUND_HALF_UP``

        """
        self.min_value = min_value
        self.max_value = max_value
        self.force_string = force_string
        self.precision = precision
        self.rounding = rounding

        super(DecimalField, self).__init__(**kwargs)

def _calc_ratio(part, whole):
    """Calculate ratio

    Returns int
    """
    return int((part / whole * 100).quantize(
        decimal.Decimal('1'), rounding=decimal.ROUND_HALF_DOWN))

def _calc_ratio(part, whole):
    """Calculate ratio

    Returns int
    """
    return int((part/whole*100).quantize(
        decimal.Decimal('1'), rounding=decimal.ROUND_HALF_DOWN))

def _eval(self, xctx: XPathContext) -> float:
        dec = decimal.Decimal(self.expr._eval_float(xctx))
        try:
            return float(dec.to_integral_value(
                decimal.ROUND_HALF_UP if dec > 0 else decimal.ROUND_HALF_DOWN))
        except decimal.InvalidOperation:
            return float('nan')

def _calc_ratio(part, whole):
    """Calculate ratio

    Returns int
    """
    return int((part/whole*100).quantize(
        decimal.Decimal('1'), rounding=decimal.ROUND_HALF_DOWN))