Fix the fraction module so that __rpow__ works on arbitrary classes.

The fraction module implicitly casted float if __rpow__ was implemented in your class when raising a fraction to a power. Now it isn't done but will raise an exception if __rpow__ isn't implemented.

Author: zitterbewegung

Doc/library/functions.rst

@@ -608,9 +608,13 @@ are always available.  They are listed here in alphabetical order.
    will be used for both the global and the local variables.  If *globals* and
    *locals* are given, they are used for the global and local variables,
    respectively.  If provided, *locals* can be any mapping object.  Remember
-   that at the module level, globals and locals are the same dictionary. If exec
-   gets two separate objects as *globals* and *locals*, the code will be
-   executed as if it were embedded in a class definition.
+   that at the module level, globals and locals are the same dictionary.
+
+   .. note::
+
+      Most users should just pass a *globals* argument and never *locals*.
+      If exec gets two separate objects as *globals* and *locals*, the code
+      will be executed as if it were embedded in a class definition.
 
    If the *globals* dictionary does not contain a value for the key
    ``__builtins__``, a reference to the dictionary of the built-in module

Lib/fractions.py

@@ -875,8 +875,10 @@ def __pow__(a, b):
                 # A fractional power will generally produce an
                 # irrational number.
                 return float(a) ** float(b)
-        else:
+        elif isinstance(b, (float, complex)):
             return float(a) ** b
+        else:
+            return NotImplemented
 
     def __rpow__(b, a):
         """a ** b"""

Misc/ACKS

@@ -751,6 +751,7 @@ Kasun Herath
 Chris Herborth
 Ivan Herman
 Jürgen Hermann
+Joshua Jay Herman
 Gary Herron
 Ernie Hershey
 Thomas Herve

Misc/NEWS.d/next/Library/2024-05-20-13-48-37.gh-issue-119189.dhJVs5.rst

@@ -0,0 +1,3 @@
+This fixes a situation where raising a class with rpow in the class calling
+the exponent operator to raise it to the power of that class to not cast it
+as a float.