Index: Misc/NEWS
===================================================================
--- Misc/NEWS	(revision 82559)
+++ Misc/NEWS	(working copy)
@@ -1394,6 +1394,9 @@
 Extension Modules
 -----------------
 
+- Add new functions math.isfinite and cmath.isfinite, to round out
+  existing isinf and isnan functions.
+
 - In the math module, correctly lookup __trunc__, __ceil__, and __floor__ as
   special methods.
 
Index: Doc/library/cmath.rst
===================================================================
--- Doc/library/cmath.rst	(revision 82559)
+++ Doc/library/cmath.rst	(working copy)
@@ -187,6 +187,11 @@
 Classification functions
 ------------------------
 
+.. function:: isfinite(x)
+
+   Return ``True`` if both the real and imaginary parts of *x* are finite,
+   and ``False`` otherwise.
+
 .. function:: isinf(x)
 
    Return *True* if the real or the imaginary part of x is positive
Index: Doc/library/math.rst
===================================================================
--- Doc/library/math.rst	(revision 82559)
+++ Doc/library/math.rst	(working copy)
@@ -97,6 +97,12 @@
    <http://code.activestate.com/recipes/393090/>`_\.
 
 
+.. function:: isfinite(x)
+
+   Return ``True`` if *x* is neither an infinity nor a nan, and
+   ``False`` otherwise.  (Note that 0.0 *is* considered finite.)
+
+
 .. function:: isinf(x)
 
    Check if the float *x* is positive or negative infinity.
Index: Lib/test/test_math.py
===================================================================
--- Lib/test/test_math.py	(revision 82559)
+++ Lib/test/test_math.py	(working copy)
@@ -930,6 +930,15 @@
         #self.assertEquals((), math.trunc(t))
         #self.assertRaises(TypeError, math.trunc, t, 0)
 
+    def testIsfinite(self):
+        self.assertTrue(math.isfinite(0.0))
+        self.assertTrue(math.isfinite(-0.0))
+        self.assertTrue(math.isfinite(1.0))
+        self.assertTrue(math.isfinite(-1.0))
+        self.assertFalse(math.isfinite(float("nan")))
+        self.assertFalse(math.isfinite(float("inf")))
+        self.assertFalse(math.isfinite(float("-inf")))
+
     def testIsnan(self):
         self.assertTrue(math.isnan(float("nan")))
         self.assertTrue(math.isnan(float("inf")* 0.))
Index: Lib/test/test_cmath.py
===================================================================
--- Lib/test/test_cmath.py	(revision 82559)
+++ Lib/test/test_cmath.py	(working copy)
@@ -442,6 +442,15 @@
         self.assertCEqual(rect(1, pi/2), (0, 1.))
         self.assertCEqual(rect(1, -pi/2), (0, -1.))
 
+    def test_isfinite(self):
+        real_vals = [float('-inf'), -2.3, -0.0,
+                     0.0, 2.3, float('inf'), float('nan')]
+        for x in real_vals:
+            for y in real_vals:
+                z = complex(x, y)
+                self.assertEquals(cmath.isfinite(z),
+                                  math.isfinite(x) and math.isfinite(y))
+
     def test_isnan(self):
         self.assertFalse(cmath.isnan(1))
         self.assertFalse(cmath.isnan(1j))
Index: Modules/mathmodule.c
===================================================================
--- Modules/mathmodule.c	(revision 82559)
+++ Modules/mathmodule.c	(working copy)
@@ -1822,6 +1822,19 @@
 Convert angle x from degrees to radians.");
 
 static PyObject *
+math_isfinite(PyObject *self, PyObject *arg)
+{
+    double x = PyFloat_AsDouble(arg);
+    if (x == -1.0 && PyErr_Occurred())
+        return NULL;
+    return PyBool_FromLong((long)Py_IS_FINITE(x));
+}
+
+PyDoc_STRVAR(math_isfinite_doc,
+"isfinite(x) -> bool\n\n\
+Check if float x is finite (not an infinity or NaN).");
+
+static PyObject *
 math_isnan(PyObject *self, PyObject *arg)
 {
     double x = PyFloat_AsDouble(arg);
@@ -1874,6 +1887,7 @@
     {"hypot",           math_hypot,     METH_VARARGS,   math_hypot_doc},
     {"isinf",           math_isinf,     METH_O,         math_isinf_doc},
     {"isnan",           math_isnan,     METH_O,         math_isnan_doc},
+    {"isfinite",        math_isfinite,  METH_O,      math_isfinite_doc},
     {"ldexp",           math_ldexp,     METH_VARARGS,   math_ldexp_doc},
     {"lgamma",          math_lgamma,    METH_O,         math_lgamma_doc},
     {"log",             math_log,       METH_VARARGS,   math_log_doc},
Index: Modules/cmathmodule.c
===================================================================
--- Modules/cmathmodule.c	(revision 82559)
+++ Modules/cmathmodule.c	(working copy)
@@ -1024,6 +1024,19 @@
 Convert from polar coordinates to rectangular coordinates.");
 
 static PyObject *
+cmath_isfinite(PyObject *self, PyObject *args)
+{
+    Py_complex z;
+    if (!PyArg_ParseTuple(args, "D:isfinite", &z))
+        return NULL;
+    return PyBool_FromLong(Py_IS_FINITE(z.real) && Py_IS_FINITE(z.imag));
+}
+
+PyDoc_STRVAR(cmath_isfinite_doc,
+"isfinite(z) -> bool\n\
+Return True if both the real and imaginary parts of z are finite, else False.");
+
+static PyObject *
 cmath_isnan(PyObject *self, PyObject *args)
 {
     Py_complex z;
@@ -1065,6 +1078,7 @@
     {"cos",    cmath_cos,   METH_VARARGS, c_cos_doc},
     {"cosh",   cmath_cosh,  METH_VARARGS, c_cosh_doc},
     {"exp",    cmath_exp,   METH_VARARGS, c_exp_doc},
+    {"isfinite",cmath_isfinite, METH_VARARGS, cmath_isfinite_doc},
     {"isinf",  cmath_isinf, METH_VARARGS, cmath_isinf_doc},
     {"isnan",  cmath_isnan, METH_VARARGS, cmath_isnan_doc},
     {"log",    cmath_log,   METH_VARARGS, cmath_log_doc},