diff -r 2f563908ebc5 Modules/zlibmodule.c
--- a/Modules/zlibmodule.c	Thu Apr 26 17:05:31 2012 +0200
+++ b/Modules/zlibmodule.c	Fri Apr 27 13:33:57 2012 -0700
@@ -916,6 +916,67 @@
     return retval;
 }
 
+PyDoc_STRVAR(decomp_set_dictionary__doc__,
+"set_dictionary(dict) -- Initialize the compression dictionary.\n");
+
+static PyObject *
+PyZlib_decomp_set_dictionary(compobject *self, PyObject *args)
+{
+    int err, dlen;
+    Byte *dict;
+    PyObject * retval = NULL;
+
+    if (!PyArg_ParseTuple(args, "s#|i:set_dictionary", &dict, &dlen)) {
+        return NULL;
+    }
+
+    ENTER_ZLIB(self);
+
+    Py_BEGIN_ALLOW_THREADS
+    err = deflateSetDictionary (&(self->zst), dict, dlen);
+    Py_END_ALLOW_THREADS
+
+    if (err == Z_OK) {
+      Py_INCREF (Py_None);
+      retval = Py_None;
+    } else {
+      zlib_error (self->zst, err, "from deflateSetDictionary()");
+    }
+
+    LEAVE_ZLIB(self);
+      
+    return retval;
+}
+
+static PyObject *
+PyZlib_comp_set_dictionary(compobject *self, PyObject *args)
+{
+    int err, dlen;
+    Byte *dict;
+    PyObject * retval = NULL;
+
+    if (!PyArg_ParseTuple(args, "s#|i:set_dictionary", &dict, &dlen)) {
+        return NULL;
+    }
+
+    ENTER_ZLIB(self);
+
+    Py_BEGIN_ALLOW_THREADS
+    err = inflateSetDictionary (&(self->zst), dict, dlen);
+    Py_END_ALLOW_THREADS
+
+    if (err == Z_OK) {
+      Py_INCREF (Py_None);
+      retval = Py_None;
+    } else {
+      zlib_error (self->zst, err, "from inflateSetDictionary()");
+    }
+
+    LEAVE_ZLIB(self);
+      
+    return retval;
+}
+
 static PyMethodDef comp_methods[] =
 {
     {"compress", (binaryfunc)PyZlib_objcompress, METH_VARARGS,
@@ -926,6 +987,8 @@
     {"copy",  (PyCFunction)PyZlib_copy, METH_NOARGS,
               comp_copy__doc__},
 #endif
+    {"set_dictionary", (PyCFunction)PyZlib_decomp_set_dictionary, METH_VARARGS,
+                       decomp_set_dictionary__doc__},
     {NULL, NULL}
 };
 
@@ -939,6 +1002,8 @@
     {"copy",  (PyCFunction)PyZlib_uncopy, METH_NOARGS,
               decomp_copy__doc__},
 #endif
+    {"set_dictionary", (PyCFunction)PyZlib_comp_set_dictionary, METH_VARARGS,
+                       decomp_set_dictionary__doc__},
     {NULL, NULL}
 };