Only initialize the method dispatcher once

This has a _significant_ effect on parser creation time

Author: gsnedders

html5lib/_utils.py

@@ -2,6 +2,11 @@
 
 from types import ModuleType
 
+try:
+    from collections.abc import Mapping
+except ImportError:
+    from collections import Mapping
+
 from six import text_type
 
 try:
@@ -65,6 +70,41 @@ def __getitem__(self, key):
         return dict.get(self, key, self.default)
 
 
+class BoundMethodDispatcher(Mapping):
+    def __init__(self, instance, dispatcher):
+        self.instance = instance
+        self.dispatcher = dispatcher
+        self.cache = {}
+
+    def __getitem__(self, key):
+        if key in self.cache:
+            return self.cache[key]
+
+        try:
+            item = self.dispatcher[key]
+        except KeyError:
+            item = self.default
+
+        r = item.__get__(self.instance)
+        self.cache[key] = r
+        return r
+
+    def get(self, key, default):
+        if key in self.dispatcher:
+            return self[key]
+        else:
+            return default
+
+    def __iter__(self):
+        return iter(self.dispatcher)
+
+    def __len__(self):
+        return len(self.dispatcher)
+
+    def __contains__(self, key):
+        return key in self.dispatcher
+
+
 # Some utility functions to deal with weirdness around UCS2 vs UCS4
 # python builds