From e5587cf234684d095516a5881f4d829deceb2cd2 Mon Sep 17 00:00:00 2001
From: Mike Croucher <michael.p.croucher@googlemail.com>
Date: Fri, 13 Mar 2015 14:43:49 +0000
Subject: [PATCH] Used 'six' to support Py3 and Py2 simultaneously

---
 GPy/core/parameterization/parameterized.py | 10 ++++++----
 GPy/kern/_src/kern.py                      | 11 ++++++-----
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/GPy/core/parameterization/parameterized.py b/GPy/core/parameterization/parameterized.py
index 27ecbc1c..691bf4a7 100644
--- a/GPy/core/parameterization/parameterized.py
+++ b/GPy/core/parameterization/parameterized.py
@@ -1,7 +1,7 @@
 # Copyright (c) 2014, Max Zwiessele, James Hensman
 # Licensed under the BSD 3-clause license (see LICENSE.txt)
 
-
+import six # For metaclass support in Python 2 and 3 simultaneously
 import numpy; np = numpy
 import itertools
 from re import compile, _pattern_type
@@ -27,7 +27,8 @@ class ParametersChangedMeta(type):
         self.parameters_changed()
         return self
 
-class Parameterized(Parameterizable,metaclass=ParametersChangedMeta):
+@six.add_metaclass(ParametersChangedMeta)
+class Parameterized(Parameterizable):
     """
     Parameterized class
 
@@ -73,8 +74,9 @@ class Parameterized(Parameterizable,metaclass=ParametersChangedMeta):
     # Metaclass for parameters changed after init.
     # This makes sure, that parameters changed will always be called after __init__
     # **Never** call parameters_changed() yourself
-    #This is ignored in Python 3 -- you need to put the meta class in the 
-    __metaclass__ = ParametersChangedMeta
+    #This is ignored in Python 3 -- you need to put the meta class in the function definition. 
+    #__metaclass__ = ParametersChangedMeta
+    #The six module is used to support both Python 2 and 3 simultaneously
     #===========================================================================
     def __init__(self, name=None, parameters=[], *a, **kw):
         super(Parameterized, self).__init__(name=name, *a, **kw)
diff --git a/GPy/kern/_src/kern.py b/GPy/kern/_src/kern.py
index 2e8ebcb0..e63ddad4 100644
--- a/GPy/kern/_src/kern.py
+++ b/GPy/kern/_src/kern.py
@@ -8,15 +8,16 @@ from .kernel_slice_operations import KernCallsViaSlicerMeta
 from ...util.caching import Cache_this
 from GPy.core.parameterization.observable_array import ObsAr
 from functools import reduce
+import six
 
-
-
-class Kern(Parameterized,metaclass=KernCallsViaSlicerMeta):
+@six.add_metaclass(KernCallsViaSlicerMeta)
+class Kern(Parameterized):
     #===========================================================================
     # This adds input slice support. The rather ugly code for slicing can be
     # found in kernel_slice_operations
-    # __mataclass__ is ignored in Python 3 - needs to be put in the function definiton
-    __metaclass__ = KernCallsViaSlicerMeta
+    # __meataclass__ is ignored in Python 3 - needs to be put in the function definiton
+    #__metaclass__ = KernCallsViaSlicerMeta
+    #Here, we use the Python module six to support Py3 and Py2 simultaneously
     #===========================================================================
     _support_GPU=False
     def __init__(self, input_dim, active_dims, name, useGPU=False, *a, **kw):