decimal.py 文件源码

def logb(self, context=None):
        """ Returns the exponent of the magnitude of self's MSD.

        The result is the integer which is the exponent of the magnitude
        of the most significant digit of self (as though it were truncated
        to a single digit while maintaining the value of that digit and
        without limiting the resulting exponent).
        """
        # logb(NaN) = NaN
        ans = self._check_nans(context=context)
        if ans:
            return ans

        if context is None:
            context = getcontext()

        # logb(+/-Inf) = +Inf
        if self._isinfinity():
            return _Infinity

        # logb(0) = -Inf, DivisionByZero
        if not self:
            return context._raise_error(DivisionByZero, 'logb(0)', 1)

        # otherwise, simply return the adjusted exponent of self, as a
        # Decimal.  Note that no attempt is made to fit the result
        # into the current context.
        ans = Decimal(self.adjusted())
        return ans._fix(context)