From 20a6e95c0caa6671d1e8a87c0fce85f3a6c56451 Mon Sep 17 00:00:00 2001
From: Robin De Schepper <robin.deschepper93gmail.com>
Date: Sat, 20 Mar 2021 18:03:11 +0100
Subject: [PATCH] Apply changes only to Python 3.6+ where metaclass alternative
 is availbl

---
 share/lib/python/neuron/__init__.py |  5 +++-
 share/lib/python/neuron/hclass35.py | 40 +++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)
 create mode 100644 share/lib/python/neuron/hclass35.py

diff --git a/share/lib/python/neuron/__init__.py b/share/lib/python/neuron/__init__.py
index cbad1d1e56..a608e285f8 100644
--- a/share/lib/python/neuron/__init__.py
+++ b/share/lib/python/neuron/__init__.py
@@ -242,7 +242,10 @@ def test_rxd(exitOnError=True):
   from neuron.hclass2 import hclass
 else:
   sys.modules["neuron.hclass2"] = types.ModuleType("neuron.hclass2")
-  from neuron.hclass3 import HocBaseObject, hclass, nonlocal_hclass
+  if sys.version_info[0] == 3 and sys.version_info[1] < 6:
+    from neuron.hclass35 import hclass
+  else:
+    from neuron.hclass import HocBaseObject, hclass, nonlocal_hclass
 
 # global list of paths already loaded by load_mechanisms
 nrn_dll_loaded = []
diff --git a/share/lib/python/neuron/hclass35.py b/share/lib/python/neuron/hclass35.py
new file mode 100644
index 0000000000..98c014f0f1
--- /dev/null
+++ b/share/lib/python/neuron/hclass35.py
@@ -0,0 +1,40 @@
+#Python 3.0-3.5 only
+# ------------------------------------------------------------------------------
+# class factory for subclassing h.anyclass
+# h.anyclass methods may be overridden. If so the base method can be called
+# using the idiom self.basemethod = self.baseattr('methodname')
+# ------------------------------------------------------------------------------
+
+from neuron import h, hoc
+import nrn
+
+#avoid syntax error if compiled by python 2
+
+class MetaHocObject(type):
+  """Provides Exception for Inheritance of multiple HocObject"""
+  def __new__(cls, name, bases, attrs):
+    #print cls, name, bases
+    m = []
+    for b in bases:
+      if issubclass(b, hoc.HocObject):
+        m.append(b.__name__)
+    if (len(m) > 1):
+      raise TypeError('Multiple Inheritance of HocObject in %s' % name
+        + ' through %s not allowed' % ','.join(m))
+      #note that join(b.__name__ for b in m) is not valid for Python 2.3
+
+    return type.__new__(cls, name, bases, attrs)
+
+def hclass(c):
+    """Class factory for subclassing h.anyclass. E.g. class MyList(hclass(h.List)):..."""
+    if c == h.Section :
+        return nrn.Section
+    class hc(hoc.HocObject, metaclass=MetaHocObject):
+    #class hc(hoc.HocObject):
+        def __new__(cls, *args, **kwds):
+            kwds2 = {'hocbase': cls.htype}
+            if 'sec' in kwds:
+                kwds2['sec'] = kwds['sec']
+            return hoc.HocObject.__new__(cls, *args, **kwds2)
+    setattr(hc, 'htype', c)
+    return hc