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| -rw-r--r-- | Doc/library/decimal.rst | 65 |
1 files changed, 45 insertions, 20 deletions
diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst index be8f41d713..2dcd44572b 100644 --- a/Doc/library/decimal.rst +++ b/Doc/library/decimal.rst @@ -128,6 +128,8 @@ representation error). Decimal numbers include special values such as Decimal("3.14") >>> Decimal(str(2.0 ** 0.5)) Decimal("1.41421356237") + >>> Decimal(2) ** Decimal("0.5") + Decimal("1.414213562373095048801688724") >>> Decimal("NaN") Decimal("NaN") >>> Decimal("-Infinity") @@ -177,6 +179,17 @@ floating point flying circus:: >>> c % a Decimal("0.77") +And some mathematic functions are also available to Decimal:: + + >>> Decimal(2).sqrt() + Decimal("1.414213562373095048801688724") + >>> Decimal(1).exp() + Decimal("2.718281828459045235360287471") + >>> Decimal("10").ln() + Decimal("2.302585092994045684017991455") + >>> Decimal("10").log10() + Decimal("1") + The :meth:`quantize` method rounds a number to a fixed exponent. This method is useful for monetary applications that often round results to a fixed number of places:: @@ -419,6 +432,11 @@ also have a number of specialized methods: given number. The result is correctly rounded using the :const:`ROUND_HALF_EVEN` rounding mode. + >>> Decimal(1).exp() + Decimal("2.718281828459045235360287471") + >>> Decimal(321).exp() + Decimal("2.561702493119680037517373933E+139") + .. versionadded:: 2.6 .. method:: Decimal.fma(other, third[, context]) @@ -426,78 +444,82 @@ also have a number of specialized methods: Fused multiply-add. Return self*other+third with no rounding of the intermediate product self*other. + >>> Decimal(2).fma(3, 5) + Decimal("11") + .. versionadded:: 2.6 .. method:: Decimal.is_canonical() - Return ``Decimal(1)`` if the argument is canonical and - ``Decimal(0)`` otherwise. Currently, a :class:`Decimal` instance + Return :const:`True` if the argument is canonical and + :const:`False` otherwise. Currently, a :class:`Decimal` instance is always canonical, so this operation always returns - ``Decimal(1)``. + :const:`True`. .. versionadded:: 2.6 .. method:: is_finite() - Return ``Decimal(1)`` if the argument is a finite number, and - ``Decimal(0)`` if the argument is an infinity or a NaN. + Return :const:`True` if the argument is a finite number, and + :const:`False` if the argument is an infinity or a NaN. .. versionadded:: 2.6 .. method:: is_infinite() - Return ``Decimal(1)`` if the argument is either positive or - negative infinity and ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is either positive or + negative infinity and :const:`False` otherwise. .. versionadded:: 2.6 .. method:: is_nan() - Return ``Decimal(1)`` if the argument is a (quiet or signaling) - NaN and ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is a (quiet or signaling) + NaN and :const:`False` otherwise. .. versionadded:: 2.6 .. method:: is_normal() - Return ``Decimal(1)`` if the argument is a *normal* finite number. - Return ``Decimal(0)`` if the argument is zero, subnormal, infinite + Return :const:`True` if the argument is a *normal* finite number. + Return :const:`False` if the argument is zero, subnormal, infinite or a NaN. .. versionadded:: 2.6 .. method:: is_qnan() - Return ``Decimal(1)`` if the argument is a quiet NaN, and ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is a quiet NaN, and + :const:`False` otherwise. .. versionadded:: 2.6 .. method:: is_signed() - Return ``Decimal(1)`` if the argument has a negative sign and - ``Decimal(0)`` otherwise. Note that zeros and NaNs can both carry + Return :const:`True` if the argument has a negative sign and + :const:`False` otherwise. Note that zeros and NaNs can both carry signs. .. versionadded:: 2.6 .. method:: is_snan() - Return ``Decimal(1)`` if the argument is a signaling NaN and - ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is a signaling NaN and + :const:`False` otherwise. .. versionadded:: 2.6 .. method:: is_subnormal() - Return ``Decimal(1)`` if the argument is subnormal, and - ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is subnormal, and + :const:`False` otherwise. .. versionadded:: 2.6 .. method:: is_zero() - Return ``Decimal(1)`` if the argument is a (positive or negative) - zero and ``Decimal(0)`` otherwise. + Return :const:`True` if the argument is a (positive or negative) + zero and :const:`False` otherwise. .. versionadded:: 2.6 @@ -640,6 +662,9 @@ also have a number of specialized methods: Returns a value equal to the first operand after rounding and having the exponent of the second operand. + >>> Decimal("1.41421356").quantize(Decimal("1.000")) + Decimal("1.414") + Unlike other operations, if the length of the coefficient after the quantize operation would be greater than precision, then an :const:`InvalidOperation` is signaled. This guarantees that, unless |