ENH: Add ability to pickle ufuncs as requested in ticket #1743

numpy/core/__init__.py

@@ -39,3 +39,29 @@
 from numpy.testing import Tester
 test = Tester().test
 bench = Tester().bench
+
+# Make it possible so that ufuncs can be pickled
+#  Here are the loading and unloading functions
+# The name numpy.core._ufunc_reconstruct must be
+#   available for unpickling to work.
+def _ufunc_reconstruct(module, name):
+    mod = __import__(module)
+    return getattr(mod, name)
+
+def _ufunc_reduce(func):
+    from pickle import whichmodule
+    name = func.__name__
+    return _ufunc_reconstruct, (whichmodule(func,name), name)
+
+
+import sys
+if sys.version_info[0] < 3:
+    import copy_reg as copyreg
+else:
+    import copyreg
+
+copyreg.pickle(ufunc, _ufunc_reduce, _ufunc_reconstruct)
+# Unclutter namespace (must keep _ufunc_reconstruct for unpickling)
+del copyreg
+del sys
+del _ufunc_reduce

numpy/core/tests/test_ufunc.py

@@ -5,6 +5,15 @@
 import numpy.core.umath_tests as umt
 
 class TestUfunc(TestCase):
+    def test_pickle(self):
+        import pickle
+        assert pickle.loads(pickle.dumps(np.sin)) is np.sin
+
+    def test_pickle_withstring(self):
+        import pickle
+        astring = "cnumpy.core\n_ufunc_reconstruct\np0\n(S'numpy.core.umath'\np1\nS'cos'\np2\ntp3\nRp4\n."
+        assert pickle.loads(astring) is np.cos
+
     def test_reduceat_shifting_sum(self) :
         L = 6
         x = np.arange(L)