gh-92417: fractions, decimal: Improve docs for alternative constructor methods

Doc/library/decimal.rst

@@ -374,10 +374,22 @@ Decimal objects
    returns ``Decimal('1.414')``.
 
    If *value* is a :class:`float`, the binary floating point value is losslessly
-   converted to its exact decimal equivalent.  This conversion can often require
-   53 or more digits of precision.  For example, ``Decimal(float('1.1'))``
-   converts to
-   ``Decimal('1.100000000000000088817841970012523233890533447265625')``.
+   converted to its exact decimal equivalent.  This means, for example, that
+   ``Decimal(0.1)`` is not the same as ``Decimal('0.1')``.
+   Since 0.1 is not exactly representable in binary floating point, the
+   value is stored as the nearest representable value which is
+   ``0x1.999999999999ap-4``.
+
+   .. doctest::
+
+      >>> Decimal(0.1)
+      Decimal('0.1000000000000000055511151231257827021181583404541015625')
+      >>> Decimal(float('nan'))
+      Decimal('NaN')
+      >>> Decimal(float('inf'))
+      Decimal('Infinity')
+      >>> Decimal(float('-inf'))
+      Decimal('-Infinity')
 
    The *context* precision does not affect how many digits are stored. That is
    determined exclusively by the number of digits in *value*. For example,
@@ -571,29 +583,9 @@ Decimal objects
       >>> Decimal(321).exp()
       Decimal('2.561702493119680037517373933E+139')
 
-   .. method:: from_float(f)
+   .. classmethod:: from_float(f)
 
-      Classmethod that converts a float to a decimal number, exactly.
-
-      Note `Decimal.from_float(0.1)` is not the same as `Decimal('0.1')`.
-      Since 0.1 is not exactly representable in binary floating point, the
-      value is stored as the nearest representable value which is
-      `0x1.999999999999ap-4`.  That equivalent value in decimal is
-      `0.1000000000000000055511151231257827021181583404541015625`.
-
-      .. note:: From Python 3.2 onwards, a :class:`Decimal` instance
-         can also be constructed directly from a :class:`float`.
-
-      .. doctest::
-
-          >>> Decimal.from_float(0.1)
-          Decimal('0.1000000000000000055511151231257827021181583404541015625')
-          >>> Decimal.from_float(float('nan'))
-          Decimal('NaN')
-          >>> Decimal.from_float(float('inf'))
-          Decimal('Infinity')
-          >>> Decimal.from_float(float('-inf'))
-          Decimal('-Infinity')
+      Alternative constructor that only accepts instances of :class:`float`.
 
       .. versionadded:: 3.1
 

Doc/library/fractions.rst

@@ -114,29 +114,15 @@ another rational number, or from a string.
 
       .. versionadded:: 3.8
 
-   .. method:: from_float(flt)
+   .. classmethod:: from_float(flt)
 
-      This class method constructs a :class:`Fraction` representing the exact
-      value of *flt*, which must be a :class:`float`. Beware that
-      ``Fraction.from_float(0.3)`` is not the same value as ``Fraction(3, 10)``.
+      Alternative constructor which only accepts instances of
+      :class:`~numbers.Integral` or :class:`float`.
 
-      .. note::
-
-         From Python 3.2 onwards, you can also construct a
-         :class:`Fraction` instance directly from a :class:`float`.
-
-
-   .. method:: from_decimal(dec)
-
-      This class method constructs a :class:`Fraction` representing the exact
-      value of *dec*, which must be a :class:`decimal.Decimal` instance.
-
-      .. note::
-
-         From Python 3.2 onwards, you can also construct a
-         :class:`Fraction` instance directly from a :class:`decimal.Decimal`
-         instance.
+   .. classmethod:: from_decimal(dec)
 
+      Alternative constructor which only accepts instances of
+      :class:`decimal.Decimal`.
 
    .. method:: limit_denominator(max_denominator=1000000)