decimal.py 文件源码

def _convert_for_comparison(self, other, equality_op=False):
    """Given a Decimal instance self and a Python object other, return
    a pair (s, o) of Decimal instances such that "s op o" is
    equivalent to "self op other" for any of the 6 comparison
    operators "op".

    """
    if isinstance(other, Decimal):
        return self, other

    # Comparison with a Rational instance (also includes integers):
    # self op n/d <=> self*d op n (for n and d integers, d positive).
    # A NaN or infinity can be left unchanged without affecting the
    # comparison result.
    if isinstance(other, _numbers.Rational):
        if not self._is_special:
            self = _dec_from_triple(self._sign,
                                    str(int(self._int) * other.denominator),
                                    self._exp)
        return self, Decimal(other.numerator)

    # Comparisons with float and complex types.  == and != comparisons
    # with complex numbers should succeed, returning either True or False
    # as appropriate.  Other comparisons return NotImplemented.
    if equality_op and isinstance(other, _numbers.Complex) and other.imag == 0:
        other = other.real
    if isinstance(other, float):
        context = getcontext()
        if equality_op:
            context.flags[FloatOperation] = 1
        else:
            context._raise_error(FloatOperation,
                "strict semantics for mixing floats and Decimals are enabled")
        return self, Decimal.from_float(other)
    return NotImplemented, NotImplemented


##### Setup Specific Contexts ############################################

# The default context prototype used by Context()
# Is mutable, so that new contexts can have different default values