#5228: add pickle support to functools.partial

Lib/test/test_functools.py

@@ -2,6 +2,7 @@ import functools
 import unittest
 from test import test_support
 from weakref import proxy
+import pickle
 
 @staticmethod
 def PythonPartial(func, *args, **keywords):
@@ -19,6 +20,10 @@ def capture(*args, **kw):
     """capture all positional and keyword arguments"""
     return args, kw
 
+def signature(part):
+    """ return the signature of a partial object """
+    return (part.func, part.args, part.keywords, part.__dict__)
+
 class TestPartial(unittest.TestCase):
 
     thetype = functools.partial
@@ -140,6 +145,12 @@ class TestPartial(unittest.TestCase):
         join = self.thetype(''.join)
         self.assertEqual(join(data), '0123456789')
 
+    def test_pickle(self):
+        f = self.thetype(signature, 'asdf', bar=True)
+        f.add_something_to__dict__ = True
+        f_copy = pickle.loads(pickle.dumps(f))
+        self.assertEqual(signature(f), signature(f_copy))
+
 class PartialSubclass(functools.partial):
     pass
 
@@ -147,11 +158,13 @@ class TestPartialSubclass(TestPartial):
 
     thetype = PartialSubclass
 
-
 class TestPythonPartial(TestPartial):
 
     thetype = PythonPartial
 
+    # the python version isn't picklable
+    def test_pickle(self): pass
+
 class TestUpdateWrapper(unittest.TestCase):
 
     def check_wrapper(self, wrapper, wrapped,

Misc/ACKS

@@ -168,6 +168,7 @@ Roger Dev
 Raghuram Devarakonda
 Toby Dickenson
 Mark Dickinson
+Jack Diederich
 Yves Dionne
 Daniel Dittmar
 Jaromir Dolecek

Misc/NEWS

@@ -710,6 +710,8 @@ Extension Modules
 
 - Issue #4396: The parser module now correctly validates the with statement.
 
+- Issue #5228: Make functools.partial objects can now be pickled.
+
 Tests
 -----
 

Modules/_functoolsmodule.c

@@ -274,6 +274,53 @@ static PyGetSetDef partial_getsetlist[] = {
 	{NULL} /* Sentinel */
 };
 
+/* Pickle strategy:
+   __reduce__ by itself doesn't support getting kwargs in the unpickle
+   operation so we define a __setstate__ that replaces all the information
+   about the partial.  If we only replaced part of it someone would use
+   it as a hook to do stange things.
+ */
+
+PyObject *
+partial_reduce(partialobject *pto, PyObject *unused)
+{
+	return Py_BuildValue("O(O)(OOOO)", Py_TYPE(pto), pto->fn, pto->fn, 
+			     pto->args, pto->kw,
+			     pto->dict ? pto->dict : Py_None);
+}
+
+PyObject *
+partial_setstate(partialobject *pto, PyObject *args)
+{
+	PyObject *fn, *fnargs, *kw, *dict;
+	if (!PyArg_ParseTuple(args, "(OOOO):__setstate__", 
+			      &fn, &fnargs, &kw, &dict))
+		return NULL;
+	Py_XDECREF(pto->fn);
+	Py_XDECREF(pto->args);
+	Py_XDECREF(pto->kw);
+	Py_XDECREF(pto->dict);
+	pto->fn = fn;
+	pto->args = fnargs;
+	pto->kw = kw;
+	if (dict != Py_None) {
+	  pto->dict = dict;
+	  Py_INCREF(dict);
+	} else {
+	  pto->dict = NULL;
+	}
+	Py_INCREF(fn);
+	Py_INCREF(fnargs);
+	Py_INCREF(kw);
+	Py_RETURN_NONE;
+}
+
+static PyMethodDef partial_methods[] = {
+	{"__reduce__", (PyCFunction)partial_reduce, METH_NOARGS},
+	{"__setstate__", (PyCFunction)partial_setstate, METH_VARARGS},
+	{NULL,		NULL}		/* sentinel */
+};
+
 static PyTypeObject partial_type = {
 	PyVarObject_HEAD_INIT(NULL, 0)
 	"functools.partial",		/* tp_name */
@@ -304,7 +351,7 @@ static PyTypeObject partial_type = {
 	offsetof(partialobject, weakreflist),	/* tp_weaklistoffset */
 	0,				/* tp_iter */
 	0,				/* tp_iternext */
-	0,				/* tp_methods */
+	partial_methods,		/* tp_methods */
 	partial_memberlist,		/* tp_members */
 	partial_getsetlist,		/* tp_getset */
 	0,				/* tp_base */