beef up docstring

diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 5087ecc481bbef4030c3774c31ce483310029feb..01d3991d71d13eeaa8ea35e109bfc39daf1fd7ba 100644 (file)
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -630,7 +630,10 @@ error:
        return NULL;
 }
 
-PyDoc_STRVAR(math_factorial_doc, "Return n!");
+PyDoc_STRVAR(math_factorial_doc,
+"factorial(x) -> Integral\n"
+"\n"
+"Find x!. Raise a ValueError if x is negative or non-integral.");
 
 static PyObject *
 math_trunc(PyObject *self, PyObject *number)