Merge 2e1b8ed into be82756

zopefoundation · Feb 4, 2020 · d6b50a9 · d6b50a9
2 parents be82756 + 2e1b8ed
commit d6b50a9
Show file tree

Hide file tree

Showing 2 changed files with 6 additions and 0 deletions.
diff --git a/CHANGES.rst b/CHANGES.rst
@@ -67,6 +67,10 @@
   of) interface adaptation. See `issue 163
   <https://github.com/zopefoundation/zope.interface/issues/163>`_.
 
+- Fixes an possible uninitialized instance variable `_dependents` in
+  `Specification.unsubscribe`.
+  See `issue 165 <https://github.com/zopefoundation/zope.interface/issues/165>`_.
+
 4.7.1 (2019-11-11)
 ==================
 

diff --git a/src/zope/interface/interface.py b/src/zope/interface/interface.py
@@ -238,6 +238,8 @@ def subscribe(self, dependent):
         self._dependents[dependent] = self.dependents.get(dependent, 0) + 1
 
     def unsubscribe(self, dependent):
+        if self._dependents is None:
+            self._dependents = weakref.WeakKeyDictionary()
         try:
             n = self._dependents[dependent]
         except TypeError: