diff --git a/src/runtime/haskell/tests/transactions.hs b/src/runtime/haskell/tests/transactions.hs
index e9582f544..94cd91a80 100644
--- a/src/runtime/haskell/tests/transactions.hs
+++ b/src/runtime/haskell/tests/transactions.hs
@@ -36,6 +36,8 @@ main = do
       ,TestCase (assertEqual "new function type" (Just ty) (functionType gr2 "foo"))
       ,TestCase (assertEqual "old function prob" (-log 0)  (functionProbability gr1 "foo"))
       ,TestCase (assertEqual "new function prob" pi        (functionProbability gr2 "foo"))
+      ,TestCase (assertEqual "old category prob" (-log 0)  (categoryProbability gr1 "Q"))
+      ,TestCase (assertEqual "new category prob" pi        (categoryProbability gr2 "Q"))
       ]
 
   performMajorGC
diff --git a/src/runtime/python/expr.c b/src/runtime/python/expr.c
index ca5682545..b32c5cd9d 100644
--- a/src/runtime/python/expr.c
+++ b/src/runtime/python/expr.c
@@ -36,7 +36,7 @@ Type_init(TypeObject *self, PyObject *args, PyObject *kwds)
     }
     for (Py_ssize_t i = 0; i < PyList_Size(exprs); i++) {
         if (!PyObject_TypeCheck(PyList_GetItem(exprs, i), &pgf_ExprType)) {
-            PyErr_SetString(PyExc_TypeError, "invalid expression in Type_init");
+            PyErr_SetString(PyExc_TypeError, "invalid expression in Type initialisation");
             return -1;
         }
         // Py_INCREF(&exprs[i]);
@@ -353,7 +353,7 @@ Expr_unpack(ExprObject *self, PyObject *fargs)
 	for (;;) {
         if (PyObject_TypeCheck(expr, &pgf_ExprAbsType)) {
             ExprAbsObject *eabs = (ExprAbsObject *) expr;
-            PyObject* res = 
+            PyObject* res =
 				Py_BuildValue("OOOO", eabs->bind_type, eabs->name, eabs->body, args);
 			Py_DECREF(args);
             return res;
diff --git a/src/runtime/python/pypgf.c b/src/runtime/python/pypgf.c
index 3f20217d4..a24ab7f08 100644
--- a/src/runtime/python/pypgf.c
+++ b/src/runtime/python/pypgf.c
@@ -18,6 +18,22 @@ PGF_dealloc(PGFObject *self)
     Py_TYPE(self)->tp_free(self);
 }
 
+static PyObject *
+PGF_writeToFile(PGFObject *self, PyObject *args)
+{
+    const char *fpath;
+    if (!PyArg_ParseTuple(args, "s", &fpath))
+        return NULL;
+
+    PgfExn err;
+    pgf_write_pgf(fpath, self->db, self->revision, &err);
+    if (handleError(err) != PGF_EXN_NONE) {
+        return NULL;
+    }
+
+    Py_RETURN_NONE;
+}
+
 typedef struct {
     PgfItor fn;
     PGFObject *grammar;
@@ -262,6 +278,26 @@ PGF_functionIsConstructor(PGFObject *self, PyObject *args)
     return PyBool_FromLong(isCon);
 }
 
+static PyObject *
+PGF_categoryProbability(PGFObject *self, PyObject *args)
+{
+    const char *s;
+    Py_ssize_t size;
+    if (!PyArg_ParseTuple(args, "s#", &s, &size))
+        return NULL;
+
+    PgfText *catname = CString_AsPgfText(s, size);
+
+    PgfExn err;
+    prob_t prob = pgf_category_prob(self->db, self->revision, catname, &err);
+    FreePgfText(catname);
+    if (handleError(err) != PGF_EXN_NONE) {
+        return NULL;
+    }
+
+    return PyFloat_FromDouble((double)prob);
+}
+
 static PyObject *
 PGF_functionProbability(PGFObject *self, PyObject *args)
 {
@@ -307,6 +343,9 @@ static PyMemberDef PGF_members[] = {
 };
 
 static PyMethodDef PGF_methods[] = {
+    {"writeToFile", (PyCFunction)PGF_writeToFile, METH_VARARGS,
+     "Writes PGF to file"},
+
     {"categoryContext", (PyCFunction)PGF_categoryContext, METH_VARARGS,
      "Returns the context for a given category"
     },
@@ -319,6 +358,9 @@ static PyMethodDef PGF_methods[] = {
     {"functionIsConstructor", (PyCFunction)PGF_functionIsConstructor, METH_VARARGS,
      "Checks whether a function is a constructor"
     },
+    {"categoryProbability", (PyCFunction)PGF_categoryProbability, METH_VARARGS,
+     "Returns the probability of a category"
+    },
     {"functionProbability", (PyCFunction)PGF_functionProbability, METH_VARARGS,
      "Returns the probability of a function"
     },
diff --git a/src/runtime/python/tests/test_basic.py b/src/runtime/python/tests/test_basic.py
index 918ad2a32..75df99a0c 100644
--- a/src/runtime/python/tests/test_basic.py
+++ b/src/runtime/python/tests/test_basic.py
@@ -77,6 +77,12 @@ def test_newNGF_existing(NGF):
     with pytest.raises(FileExistsError):
         newNGF("empty", "./basic.ngf")
 
+# writePGF
+
+def test_writePGF(PGF):
+    PGF.writeToFile("./copy.pgf")
+    os.remove("./copy.pgf") # cleanup
+
 # abstract syntax
 
 def test_abstractName(PGF):
diff --git a/src/runtime/python/tests/test_transactions.py b/src/runtime/python/tests/test_transactions.py
index a7dfda7c0..65b20b1e3 100644
--- a/src/runtime/python/tests/test_transactions.py
+++ b/src/runtime/python/tests/test_transactions.py
@@ -70,6 +70,11 @@ def test_original_function_prob(gr1):
     #     gr1.functionProbability("foo")
     assert gr1.functionProbability("foo") == float('inf')
 
+def test_original_category_prob(gr1):
+    # with pytest.raises(KeyError):
+    #     gr1.categoryProbability("Q")
+    assert gr1.categoryProbability("Q") == float('inf')
+
 # gr2
 
 def test_extended_functions(gr2):
@@ -89,6 +94,9 @@ def test_extended_function_prob(gr2):
     # assert gr2.functionProbability("foo") == prob
     assert math.isclose(gr2.functionProbability("foo"), prob, rel_tol=1e-06)
 
+def test_extended_category_prob(gr2):
+    assert gr2.categoryProbability("Q") == prob
+
 # gr3
 
 def test_branched_functions(gr3):