From: Raymond Hettinger <python@rcn.com>
Date: Sat, 5 Jun 2004 06:16:22 +0000 (+0000)
Subject: SF bug #963956:   Bad error mesage when subclassing a module
X-Git-Tag: v2.4a1~266
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=f2c0830585a4c58c2e0cb6acbfc4efa628563c12;p=thirdparty%2FPython%2Fcpython.git

SF bug #963956:   Bad error mesage when subclassing a module

Add a more informative message for the common user mistake of subclassing
from a module name rather than another class (i.e. random instead of
random.random).
---

diff --git a/Python/ceval.c b/Python/ceval.c
index 2cebf44a4c97..2d600141f621 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -3922,6 +3922,15 @@ build_class(PyObject *methods, PyObject *bases, PyObject *name)
 	}
 	result = PyObject_CallFunction(metaclass, "OOO", name, bases, methods);
 	Py_DECREF(metaclass);
+	if (result == NULL && PyErr_ExceptionMatches(PyExc_TypeError)) {
+		/* A type error here likely means that the user passed 
+		   in a base that was not a class (such the random module
+		   instead of the random.random type).  Help them out with
+		   a more informative error message */
+		PyErr_SetString(PyExc_TypeError,
+			"Error when calling the metaclass.\n" \
+			"Make sure the base arguments are valid.");
+	}
 	return result;
 }