ldapurl.LDAPUrlExtensions: Rewrite in terms of MutableMapping

The UserDict API is not specified when it comes to extending:
it is not clear which methods can be safely overridden.

The MutableMapping ABC fixes this problem by providing an explicit
set of abstract methods, in terms of which the rest of the API
is implemented.

Switch to using MutableMapping for LDAPUrlExtensions.

Lib/ldapurl.py

@@ -16,7 +16,9 @@
   'LDAPUrlExtension','LDAPUrlExtensions','LDAPUrl'
 ]
 
-from ldap.compat import UserDict, quote, unquote
+from collections import MutableMapping
+
+from ldap.compat import quote, unquote
 
 LDAP_SCOPE_BASE = 0
 LDAP_SCOPE_ONELEVEL = 1
@@ -130,58 +132,64 @@ def __ne__(self,other):
     return not self.__eq__(other)
 
 
-class LDAPUrlExtensions(UserDict):
-  """
-  Models a collection of LDAP URL extensions as
-  dictionary type
-  """
-
-  def __init__(self,default=None):
-    UserDict.__init__(self)
-    for k,v in (default or {}).items():
-      self[k]=v
-
-  def __setitem__(self,name,value):
+class LDAPUrlExtensions(MutableMapping):
     """
-    value
-        Either LDAPUrlExtension instance, (critical,exvalue)
-        or string'ed exvalue
+    Models a collection of LDAP URL extensions as
+    a mapping type
     """
-    assert isinstance(value,LDAPUrlExtension)
-    assert name==value.extype
-    self.data[name] = value
 
-  def values(self):
-    return [
-      self[k]
-      for k in self.keys()
-    ]
-
-  def __str__(self):
-    return ','.join(str(v) for v in self.values())
-
-  def __repr__(self):
-    return '<%s.%s instance at %s: %s>' % (
-      self.__class__.__module__,
-      self.__class__.__name__,
-      hex(id(self)),
-      self.data
-    )
+    def __init__(self, default=None):
+        self._data = {}
+        if default is not None:
+            self.update(default)
+
+    def __setitem__(self, name, value):
+        """
+        value
+            Either LDAPUrlExtension instance, (critical,exvalue)
+            or string'ed exvalue
+        """
+        assert isinstance(value, LDAPUrlExtension)
+        assert name == value.extype
+        self._data[name] = value
+
+    def __getitem__(self, name):
+        return self._data[name]
+
+    def __delitem__(self, name):
+        del self._data[name]
+
+    def __iter__(self):
+        return iter(self._data)
+
+    def __len__(self):
+        return len(self._data)
+
+    def __str__(self):
+        return ','.join(str(v) for v in self.values())
+
+    def __repr__(self):
+        return '<%s.%s instance at %s: %s>' % (
+            self.__class__.__module__,
+            self.__class__.__name__,
+            hex(id(self)),
+            self._data
+        )
 
-  def __eq__(self,other):
-    assert isinstance(other,self.__class__),TypeError(
-      "other has to be instance of %s" % (self.__class__)
-    )
-    return self.data==other.data
+    def __eq__(self,other):
+        assert isinstance(other, self.__class__), TypeError(
+            "other has to be instance of %s" % (self.__class__)
+            )
+        return self._data == other._data
 
-  def parse(self,extListStr):
-    for extension_str in extListStr.strip().split(','):
-      if extension_str:
-        e = LDAPUrlExtension(extension_str)
-        self[e.extype] = e
+    def parse(self,extListStr):
+        for extension_str in extListStr.strip().split(','):
+            if extension_str:
+                e = LDAPUrlExtension(extension_str)
+                self[e.extype] = e
 
-  def unparse(self):
-    return ','.join([ v.unparse() for v in self.values() ])
+    def unparse(self):
+        return ','.join(v.unparse() for v in self.values())
 
 
 class LDAPUrl(object):