我们从Python开源项目中，提取了以下19个代码示例，用于说明如何使用decimal.Inexact()。
def dsum(iterable): "Full precision summation using Decimal objects for intermediate values" # Transform (exactly) a float to m * 2 ** e where m and e are integers. # Convert (mant, exp) to a Decimal and add to the cumulative sum. # If the precision is too small for exact conversion and addition, # then retry with a larger precision. total = Decimal(0) for x in iterable: mant, exp = frexp(x) mant, exp = int(mant * 2.0 ** 53), exp-53 while True: try: total += mant * Decimal(2) ** exp break except Inexact: getcontext().prec += 1 return float(total)
def create_decimal_from_float(self, f): """Creates a new Decimal instance from a float but rounding using self as the context. >>> context = Context(prec=5, rounding=ROUND_DOWN) >>> context.create_decimal_from_float(3.1415926535897932) Decimal('3.1415') >>> context = Context(prec=5, traps=[Inexact]) >>> context.create_decimal_from_float(3.1415926535897932) Traceback (most recent call last): ... decimal.Inexact: None """ d = Decimal.from_float(f) # An exact conversion return d._fix(self) # Apply the context rounding # Methods
def float_to_decimal(f): """ Convert a floating point number to a Decimal with no loss of information. Intended for Python 2.6 where casting float to Decimal does not work. """ n, d = f.as_integer_ratio() numerator, denominator = Decimal(n), Decimal(d) ctx = Context(prec=60) result = ctx.divide(numerator, denominator) while ctx.flags[Inexact]: ctx.flags[Inexact] = False ctx.prec *= 2 result = ctx.divide(numerator, denominator) return result
def to_integral_exact(self, rounding=None, context=None): """Rounds to a nearby integer. If no rounding mode is specified, take the rounding mode from the context. This method raises the Rounded and Inexact flags when appropriate. See also: to_integral_value, which does exactly the same as this method except that it doesn't raise Inexact or Rounded. """ if self._is_special: ans = self._check_nans(context=context) if ans: return ans return Decimal(self) if self._exp >= 0: return Decimal(self) if not self: return _dec_from_triple(self._sign, '0', 0) if context is None: context = getcontext() if rounding is None: rounding = context.rounding ans = self._rescale(0, rounding) if ans != self: context._raise_error(Inexact) context._raise_error(Rounded) return ans
def to_integral_exact(self, a): """Rounds to an integer. When the operand has a negative exponent, the result is the same as using the quantize() operation using the given operand as the left-hand-operand, 1E+0 as the right-hand-operand, and the precision of the operand as the precision setting; Inexact and Rounded flags are allowed in this operation. The rounding mode is taken from the context. >>> ExtendedContext.to_integral_exact(Decimal('2.1')) Decimal('2') >>> ExtendedContext.to_integral_exact(Decimal('100')) Decimal('100') >>> ExtendedContext.to_integral_exact(Decimal('100.0')) Decimal('100') >>> ExtendedContext.to_integral_exact(Decimal('101.5')) Decimal('102') >>> ExtendedContext.to_integral_exact(Decimal('-101.5')) Decimal('-102') >>> ExtendedContext.to_integral_exact(Decimal('10E+5')) Decimal('1.0E+6') >>> ExtendedContext.to_integral_exact(Decimal('7.89E+77')) Decimal('7.89E+77') >>> ExtendedContext.to_integral_exact(Decimal('-Inf')) Decimal('-Infinity') """ a = _convert_other(a, raiseit=True) return a.to_integral_exact(context=self)
def float_to_decimal(f): """Convert a floating point number to a Decimal with no loss of information. See: http://docs.python.org/release/2.6.7/library/decimal.html#decimal-faq """ n, d = f.as_integer_ratio() numerator, denominator = Decimal(n), Decimal(d) ctx = Context(prec=60) result = ctx.divide(numerator, denominator) while ctx.flags[Inexact]: ctx.flags[Inexact] = False ctx.prec *= 2 result = ctx.divide(numerator, denominator) return result
def next_toward(self, other, context=None): """Returns the number closest to self, in the direction towards other. The result is the closest representable number to self (excluding self) that is in the direction towards other, unless both have the same value. If the two operands are numerically equal, then the result is a copy of self with the sign set to be the same as the sign of other. """ other = _convert_other(other, raiseit=True) if context is None: context = getcontext() ans = self._check_nans(other, context) if ans: return ans comparison = self._cmp(other) if comparison == 0: return self.copy_sign(other) if comparison == -1: ans = self.next_plus(context) else: # comparison == 1 ans = self.next_minus(context) # decide which flags to raise using value of ans if ans._isinfinity(): context._raise_error(Overflow, 'Infinite result from next_toward', ans._sign) context._raise_error(Inexact) context._raise_error(Rounded) elif ans.adjusted() < context.Emin: context._raise_error(Underflow) context._raise_error(Subnormal) context._raise_error(Inexact) context._raise_error(Rounded) # if precision == 1 then we don't raise Clamped for a # result 0E-Etiny. if not ans: context._raise_error(Clamped) return ans
