Ka-Ping Yee <ping@lfw.org>:
Changes to error messages to increase consistency & clarity.

This (mostly) closes SourceForge patch #101839.
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 4ca1310..7c8cf18 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -71,7 +71,7 @@
 		if (!PyTuple_Check(alist)) {
 			if (!PySequence_Check(alist)) {
 				PyErr_SetString(PyExc_TypeError,
-				    "apply() 2nd argument must be a sequence");
+				    "apply() arg 2 must be a sequence");
 				return NULL;
 			}
 			t = PySequence_Tuple(alist);
@@ -82,7 +82,7 @@
 	}
 	if (kwdict != NULL && !PyDict_Check(kwdict)) {
 		PyErr_SetString(PyExc_TypeError,
-			   "apply() 3rd argument must be dictionary");
+			   "apply() arg 3 must be a dictionary");
 		goto finally;
 	}
 	retval = PyEval_CallObjectWithKeywords(func, alist, kwdict);
@@ -181,7 +181,7 @@
 	sqf = seq->ob_type->tp_as_sequence;
 	if (sqf == NULL || sqf->sq_length == NULL || sqf->sq_item == NULL) {
 		PyErr_SetString(PyExc_TypeError,
-			   "argument 2 to filter() must be a sequence type");
+			   "filter() arg 2 must be a sequence");
 		goto Fail_2;
 	}
 
@@ -368,7 +368,7 @@
 		start = Py_single_input;
 	else {
 		PyErr_SetString(PyExc_ValueError,
-		   "compile() mode must be 'exec' or 'eval' or 'single'");
+		   "compile() arg 3 must be 'exec' or 'eval' or 'single'");
 		return NULL;
 	}
 	return Py_CompileString(str, filename, start);
@@ -421,7 +421,7 @@
 	}
 	else if (PyObject_AsCharBuffer(v, &s, &len)) {
 		PyErr_SetString(PyExc_TypeError,
-				"complex() needs a string first argument");
+				"complex() arg is not a string");
 		return NULL;
 	}
 
@@ -431,7 +431,7 @@
 		s++;
 	if (s[0] == '\0') {
 		PyErr_SetString(PyExc_ValueError,
-				"empty string for complex()");
+				"complex() arg is an empty string");
 		return NULL;
 	}
 
@@ -445,7 +445,7 @@
 			if (s-start != len) {
 				PyErr_SetString(
 					PyExc_ValueError,
-					"null byte in argument for complex()");
+					"complex() arg contains a null byte");
 				return NULL;
 			}
 			if(!done) sw_error=1;
@@ -531,7 +531,7 @@
 
 	if (sw_error) {
 		PyErr_SetString(PyExc_ValueError,
-				"malformed string for complex()");
+				"complex() arg is a malformed string");
 		return NULL;
 	}
 
@@ -557,7 +557,7 @@
 	     ((nbi = i->ob_type->tp_as_number) == NULL ||
 	      nbi->nb_float == NULL))) {
 		PyErr_SetString(PyExc_TypeError,
-			   "complex() argument can't be converted to complex");
+			   "complex() arg can't be converted to complex");
 		return NULL;
 	}
 	/* XXX Hack to support classes with __complex__ method */
@@ -748,7 +748,7 @@
 	if (!PyString_Check(cmd) &&
 	    !PyUnicode_Check(cmd)) {
 		PyErr_SetString(PyExc_TypeError,
-			   "eval() argument 1 must be string or code object");
+			   "eval() arg 1 must be a string or code object");
 		return NULL;
 	}
 	if (PyString_AsStringAndSize(cmd, &str, NULL))
@@ -1224,7 +1224,7 @@
 					 base);
 	else {
 		PyErr_SetString(PyExc_TypeError,
-				"can't convert non-string with explicit base");
+				"int() can't convert non-string with explicit base");
 		return NULL;
 	}
 }
@@ -1257,7 +1257,7 @@
 					  base);
 	else {
 		PyErr_SetString(PyExc_TypeError,
-				"can't convert non-string with explicit base");
+				"long() can't convert non-string with explicit base");
 		return NULL;
 	}
 }
@@ -1384,7 +1384,7 @@
 	sq = v->ob_type->tp_as_sequence;
 	if (sq == NULL || sq->sq_item == NULL) {
 		PyErr_SetString(PyExc_TypeError,
-				"min() or max() of non-sequence");
+				"min() or max() arg must be a sequence");
 		return NULL;
 	}
 	w = NULL;
@@ -1417,7 +1417,7 @@
 	}
 	if (w == NULL)
 		PyErr_SetString(PyExc_ValueError,
-				"min() or max() of empty sequence");
+				"min() or max() arg is an empty sequence");
 	return w;
 }
 
@@ -1520,7 +1520,7 @@
 			ord = (long)*PyUnicode_AS_UNICODE(obj);
 	} else {
 		PyErr_Format(PyExc_TypeError,
-			     "expected string or Unicode character, " \
+			     "ord() expected string or Unicode character, " \
 			     "%.200s found", obj->ob_type->tp_name);
 		return NULL;
 	}
@@ -1528,7 +1528,7 @@
 		return PyInt_FromLong(ord);
 
 	PyErr_Format(PyExc_TypeError, 
-		     "expected a character, length-%d string found",
+		     "ord() expected a character, length-%d string found",
 		     size);
 	return NULL;
 }
@@ -1607,7 +1607,7 @@
 			return NULL;
 	}
 	if (istep == 0) {
-		PyErr_SetString(PyExc_ValueError, "zero step for range()");
+		PyErr_SetString(PyExc_ValueError, "range() arg 3 must not be zero");
 		return NULL;
 	}
 	if (istep > 0)
@@ -1617,7 +1617,7 @@
 	n = (int)bign;
 	if (bign < 0 || (long)n != bign) {
 		PyErr_SetString(PyExc_OverflowError,
-				"range() has too many items");
+				"range() result has too many items");
 		return NULL;
 	}
 	v = PyList_New(n);
@@ -1664,7 +1664,7 @@
 			return NULL;
 	}
 	if (istep == 0) {
-		PyErr_SetString(PyExc_ValueError, "zero step for xrange()");
+		PyErr_SetString(PyExc_ValueError, "xrange() arg 3 must not be zero");
 		return NULL;
 	}
 	if (istep > 0)
@@ -1673,7 +1673,7 @@
 		n = get_len_of_range(ihigh, ilow, -istep);
 	if (n < 0) {
 		PyErr_SetString(PyExc_OverflowError,
-				"xrange() has more than sys.maxint items");
+				"xrange() result has too many items");
 		return NULL;
 	}
 	return PyRange_New(ilow, n, istep, 1);
@@ -1779,7 +1779,7 @@
 	sqf = seq->ob_type->tp_as_sequence;
 	if (sqf == NULL || sqf->sq_item == NULL) {
 		PyErr_SetString(PyExc_TypeError,
-		    "2nd argument to reduce() must be a sequence object");
+		    "reduce() arg 2 must be a sequence");
 		return NULL;
 	}
 
@@ -1817,7 +1817,7 @@
 
 	if (result == NULL)
 		PyErr_SetString(PyExc_TypeError,
-			   "reduce of empty sequence with no initial value");
+			   "reduce() of empty sequence with no initial value");
 
 	return result;
 
@@ -2073,7 +2073,7 @@
 		if (icls != NULL) {
 			retval = abstract_issubclass(
 				icls, cls,
-				"second argument must be a class", 
+				"isinstance() arg 2 must be a class", 
 				1);
 			Py_DECREF(icls);
 			if (retval < 0)
@@ -2081,13 +2081,13 @@
 		}
 		else {
 			PyErr_SetString(PyExc_TypeError,
-					"second argument must be a class");
+					"isinstance() arg 2 must be a class");
 			return NULL;
 		}
 	}
         else {
 		PyErr_SetString(PyExc_TypeError,
-				"second argument must be a class");
+				"isinstance() arg 2 must be a class");
 		return NULL;
 	}
 	return PyInt_FromLong(retval);
@@ -2140,7 +2140,7 @@
 
 	if (itemsize < 1) {
 		PyErr_SetString(PyExc_TypeError,
-				"at least one sequence is required");
+				"zip() requires at least one sequence");
 		return NULL;
 	}
 	/* args must be a tuple */
diff --git a/Python/ceval.c b/Python/ceval.c
index a1c8190..df057b7 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -61,9 +61,9 @@
 static void format_exc_check_arg(PyObject *, char *, PyObject *);
 
 #define NAME_ERROR_MSG \
-	"There is no variable named '%s'"
+	"name '%.200s' is not defined"
 #define UNBOUNDLOCAL_ERROR_MSG \
-	"Local variable '%.200s' referenced before assignment"
+	"local variable '%.200s' referenced before assignment"
 
 /* Dynamic execution profile */
 #ifdef DYNAMIC_EXECUTION_PROFILE
@@ -439,8 +439,10 @@
 		if (argcount > co->co_argcount) {
 			if (!(co->co_flags & CO_VARARGS)) {
 				PyErr_Format(PyExc_TypeError,
-				"too many arguments; expected %d, got %d",
-					     co->co_argcount, argcount);
+				    "too many arguments to %s(); "
+				    "expected %d, got %d",
+				    PyString_AsString(co->co_name),
+				    co->co_argcount, argcount);
 				goto fail;
 			}
 			n = co->co_argcount;
@@ -483,7 +485,9 @@
 			if (j >= co->co_argcount) {
 				if (kwdict == NULL) {
 					PyErr_Format(PyExc_TypeError,
-					 "unexpected keyword argument: %.400s",
+					    "%.200s() got an unexpected "
+					    "keyword argument '%.400s'",
+					    PyString_AsString(co->co_name),
 					    PyString_AsString(keyword));
 					goto fail;
 				}
@@ -492,8 +496,10 @@
 			else {
 				if (GETLOCAL(j) != NULL) {
 					PyErr_Format(PyExc_TypeError, 
-				     "keyword parameter redefined: %.400s",
-					     PyString_AsString(keyword));
+					     "keyword parameter '%.400s' "
+					     "redefined in call to %.200s()",
+					     PyString_AsString(keyword),
+					     PyString_AsString(co->co_name));
 					goto fail;
 				}
 				Py_INCREF(value);
@@ -505,8 +511,10 @@
 			for (i = argcount; i < m; i++) {
 				if (GETLOCAL(i) == NULL) {
 					PyErr_Format(PyExc_TypeError,
-				"not enough arguments; expected %d, got %d",
-						     m, i);
+					    "not enough arguments to "
+					    "%.200s(); expected %d, got %d",
+					    PyString_AsString(co->co_name),
+					    m, i);
 					goto fail;
 				}
 			}
@@ -525,8 +533,9 @@
 	}
 	else {
 		if (argcount > 0 || kwcount > 0) {
-			PyErr_SetString(PyExc_TypeError,
-					"no arguments expected");
+			PyErr_Format(PyExc_TypeError,
+				     "%.200s() expected no arguments",
+				     PyString_AsString(co->co_name));
 			goto fail;
 		}
 	}
@@ -565,7 +574,7 @@
 	if (++tstate->recursion_depth > recursion_limit) {
 		--tstate->recursion_depth;
 		PyErr_SetString(PyExc_RuntimeError,
-				"Maximum recursion depth exceeded");
+				"maximum recursion depth exceeded");
 		tstate->frame = f->f_back;
 		Py_DECREF(f);
 		return NULL;
@@ -1825,7 +1834,7 @@
                                   /* Handy-dandy */ ;
 			    else {
 				PyErr_SetString(PyExc_TypeError,
-	    "unbound method must be called with class instance 1st argument");
+	    "unbound method must be called with instance as first argument");
 				x = NULL;
 				break;
 			    }
@@ -1908,9 +1917,10 @@
 				PyObject *key = POP();
 				if (PyDict_GetItem(kwdict, key) != NULL) {
 				    err = 1;
-				    PyErr_Format(PyExc_TypeError,
-					"keyword parameter redefined: %.400s",
-						 PyString_AsString(key));
+				    PyErr_Format(PyExc_TypeError, 
+					 "keyword parameter '%.400s' "
+					 "redefined in function call",
+					 PyString_AsString(key));
 				    Py_DECREF(key);
 				    Py_DECREF(value);
 				    goto extcall_fail;
@@ -2308,7 +2318,7 @@
 	}
 	else if (tb != NULL && !PyTraceBack_Check(tb)) {
 		PyErr_SetString(PyExc_TypeError,
-			   "raise 3rd arg must be traceback or None");
+			   "raise: arg 3 must be a traceback or None");
 		goto raise_error;
 	}
 
@@ -2630,6 +2640,7 @@
 call_builtin(PyObject *func, PyObject *arg, PyObject *kw)
 {
 	if (PyCFunction_Check(func)) {
+		PyCFunctionObject* f = (PyCFunctionObject*) func;
 		PyCFunction meth = PyCFunction_GetFunction(func);
 		PyObject *self = PyCFunction_GetSelf(func);
 		int flags = PyCFunction_GetFlags(func);
@@ -2643,8 +2654,9 @@
 		if (flags & METH_KEYWORDS)
 			return (*(PyCFunctionWithKeywords)meth)(self, arg, kw);
 		if (kw != NULL && PyDict_Size(kw) != 0) {
-			PyErr_SetString(PyExc_TypeError,
-				   "this function takes no keyword arguments");
+			PyErr_Format(PyExc_TypeError,
+				"%.200s() takes no keyword arguments",
+				f->m_ml->ml_name);
 			return NULL;
 		}
 		return (*meth)(self, arg);
@@ -2653,11 +2665,13 @@
 		return PyInstance_New(func, arg, kw);
 	}
 	if (PyInstance_Check(func)) {
-	        PyObject *res, *call = PyObject_GetAttrString(func,"__call__");
+	        PyObject *res, *call = PyObject_GetAttrString(func, "__call__");
 		if (call == NULL) {
+			PyInstanceObject *inst = (PyInstanceObject*) func;
 			PyErr_Clear();
-			PyErr_SetString(PyExc_AttributeError,
-				   "no __call__ method defined");
+			PyErr_Format(PyExc_AttributeError,
+				"%.200s instance has no __call__ method",
+				PyString_AsString(inst->in_class->cl_name));
 			return NULL;
 		}
 		res = PyEval_CallObjectWithKeywords(call, arg, kw);
@@ -2703,7 +2717,7 @@
 			}
 			if (self == NULL) {
 				PyErr_SetString(PyExc_TypeError,
-	   "unbound method must be called with class instance 1st argument");
+	   "unbound method must be called with instance as first argument");
 				return NULL;
 			}
 			Py_INCREF(arg);
@@ -2849,7 +2863,7 @@
 			}
 		} else {
 			PyErr_SetString(PyExc_TypeError,
-					"slice index must be int");
+					"slice indices must be integers");
 			return 0;
 		}
 		/* Truncate -- very long indices are truncated anyway */
@@ -2935,7 +2949,7 @@
 	PyObject *w, *x;
 	if (!PyModule_Check(v)) {
 		PyErr_SetString(PyExc_TypeError,
-				"import-from requires module object");
+				"import-from requires a module object");
 		return NULL;
 	}
 	w = PyModule_GetDict(v); /* TDB: can this not fail ? */
@@ -2958,7 +2972,7 @@
 
 	if (!PyModule_Check(v)) {
 		PyErr_SetString(PyExc_TypeError,
-				"import-from requires module object");
+				"import-from requires a module object");
 		return -1;
 	}
 	w = PyModule_GetDict(v); /* TBD: can this not fail ? */
@@ -3068,12 +3082,17 @@
 	    !PyCode_Check(prog) &&
 	    !PyFile_Check(prog)) {
 		PyErr_SetString(PyExc_TypeError,
-			   "exec 1st arg must be string, code or file object");
+			   "exec: arg 1 must be a string, file, or code object");
 		return -1;
 	}
-	if (!PyDict_Check(globals) || !PyDict_Check(locals)) {
+	if (!PyDict_Check(globals)) {
 		PyErr_SetString(PyExc_TypeError,
-		    "exec 2nd/3rd args must be dict or None");
+		    "exec: arg 2 must be a dictionary or None");
+		return -1;
+	}
+	if (!PyDict_Check(locals)) {
+		PyErr_SetString(PyExc_TypeError,
+		    "exec: arg 3 must be a dictionary or None");
 		return -1;
 	}
 	if (PyDict_GetItemString(globals, "__builtins__") == NULL)
diff --git a/Python/errors.c b/Python/errors.c
index 28dfbbe..3053e00 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -224,7 +224,7 @@
 PyErr_BadArgument(void)
 {
 	PyErr_SetString(PyExc_TypeError,
-			"illegal argument type for built-in operation");
+			"bad argument type for built-in operation");
 	return 0;
 }
 
diff --git a/Python/exceptions.c b/Python/exceptions.c
index 6d6291c..a95817c 100644
--- a/Python/exceptions.c
+++ b/Python/exceptions.c
@@ -188,7 +188,7 @@
 	/* Watch out for being called to early in the bootstrapping process */
 	if (PyExc_TypeError) {
 	    PyErr_SetString(PyExc_TypeError,
-	     "unbound method must be called with class instance 1st argument");
+	     "unbound method must be called with instance as first argument");
 	}
         return NULL;
     }