py23.py 文件源码

def round2(number, ndigits=None):
        """
        Implementation of Python 2 built-in round() function.

        Rounds a number to a given precision in decimal digits (default
        0 digits). The result is a floating point number. Values are rounded
        to the closest multiple of 10 to the power minus ndigits; if two
        multiples are equally close, rounding is done away from 0.

        ndigits may be negative.

        See Python 2 documentation:
        https://docs.python.org/2/library/functions.html?highlight=round#round
        """
        if ndigits is None:
            ndigits = 0

        if ndigits < 0:
            exponent = 10 ** (-ndigits)
            quotient, remainder = divmod(number, exponent)
            if remainder >= exponent//2 and number >= 0:
                quotient += 1
            return float(quotient * exponent)
        else:
            exponent = _decimal.Decimal('10') ** (-ndigits)

            d = _decimal.Decimal.from_float(number).quantize(
                exponent, rounding=_decimal.ROUND_HALF_UP)

            return float(d)