newround.py 文件源码

def newround(number, ndigits=None):
    """
    See Python 3 documentation: uses Banker's Rounding.

    Delegates to the __round__ method if for some reason this exists.

    If not, rounds a number to a given precision in decimal digits (default
    0 digits). This returns an int when called with one argument,
    otherwise the same type as the number. ndigits may be negative.

    See the test_round method in future/tests/test_builtins.py for
    examples.
    """
    return_int = False
    if ndigits is None:
        return_int = True
        ndigits = 0
    if hasattr(number, '__round__'):
        return number.__round__(ndigits)

    if ndigits < 0:
        raise NotImplementedError('negative ndigits not supported yet')
    exponent = Decimal('10') ** (-ndigits)

    if PYPY:
        # Work around issue #24: round() breaks on PyPy with NumPy's types
        if 'numpy' in repr(type(number)):
            number = float(number)

    if not PY26:
        d = Decimal.from_float(number).quantize(exponent,
                                            rounding=ROUND_HALF_EVEN)
    else:
        d = from_float_26(number).quantize(exponent, rounding=ROUND_HALF_EVEN)

    if return_int:
        return int(d)
    else:
        return float(d)


### From Python 2.7's decimal.py. Only needed to support Py2.6: