backend_pgf: implement subset of WeakSet for supporting py2.6

pwuertz · pwuertz · commit 510ca3820e94 · 2012-10-02T11:07:11.000+02:00
diff --git a/lib/matplotlib/backends/backend_pgf.py b/lib/matplotlib/backends/backend_pgf.py
@@ -223,14 +223,31 @@ def get_latex_manager():
             LatexManagerFactory.previous_instance = new_inst
             return new_inst
 
+class WeakSet:
+    # TODO: Poor man's weakref.WeakSet.
+    #       Remove this once python 2.6 support is dropped from matplotlib.
+
+    def __init__(self):
+        self.weak_key_dict = weakref.WeakKeyDictionary()
+
+    def add(self, item):
+        self.weak_key_dict[item] = None
+
+    def discard(self, item):
+        if item in self.weak_key_dict:
+            del self.weak_key_dict[item]
+
+    def __iter__(self):
+        return  self.weak_key_dict.iterkeys()
+
 
 class LatexManager:
     """
     The LatexManager opens an instance of the LaTeX application for
     determining the metrics of text elements. The LaTeX environment can be
     modified by setting fonts and/or a custem preamble in the rc parameters.
     """
-    _unclean_instances = weakref.WeakSet()
+    _unclean_instances = WeakSet()
 
     @staticmethod
     def _build_latex_header():
