Issue #21193: Make (e.g.,) pow(2, -3, 5) raise ValueError rather than TypeError. Patch by Josh Rosenberg.

Lib/test/test_builtin.py

@@ -1085,7 +1085,7 @@ class BuiltinTest(unittest.TestCase):
                     if isinstance(x, float) or \
                        isinstance(y, float) or \
                        isinstance(z, float):
-                        self.assertRaises(TypeError, pow, x, y, z)
+                        self.assertRaises(ValueError, pow, x, y, z)
                     else:
                         self.assertAlmostEqual(pow(x, y, z), 24.0)
 

Misc/ACKS

@@ -1111,6 +1111,7 @@ Armin Ronacher
 Case Roole
 Timothy Roscoe
 Erik Rose
+Josh Rosenberg
 Jim Roskind
 Brian Rosner
 Guido van Rossum

Misc/NEWS

@@ -10,6 +10,9 @@ Release date: TBA
 Core and Builtins
 -----------------
 
+- Issue #21193: pow(a, b, c) now raises ValueError rather than TypeError when b
+  is negative.  Patch by Josh Rosenberg.
+
 - PEP 465 and Issue #21176: Add the '@' operator for matrix multiplication.
 
 - Issue #21134: Fix segfault when str is called on an uninitialized

Objects/longobject.c

@@ -3841,7 +3841,7 @@ long_pow(PyObject *v, PyObject *w, PyObject *x)
 
     if (Py_SIZE(b) < 0) {  /* if exponent is negative */
         if (c) {
-            PyErr_SetString(PyExc_TypeError, "pow() 2nd argument "
+            PyErr_SetString(PyExc_ValueError, "pow() 2nd argument "
                             "cannot be negative when 3rd argument specified");
             goto Error;
         }