Adding slave context delete ability

- Fixes #20

pymodbus/datastore/context.py

@@ -120,19 +120,28 @@ def __contains__(self, slave):
         return slave in self.__slaves
 
     def __setitem__(self, slave, context):
-        ''' Wrapper used to access the slave context
+        ''' Used to set a new slave context
 
-        :param slave: slave The context to set
+        :param slave: The slave context to set
         :param context: The new context to set for this slave
         '''
         if self.single: slave = Defaults.UnitId
         if 0xf7 >= slave >= 0x00:
             self.__slaves[slave] = context
         else: raise ParameterException('slave index out of range')
 
-    def __getitem__(self, slave):
+    def __delitem__(self, slave):
         ''' Wrapper used to access the slave context
 
+        :param slave: The slave context to remove
+        '''
+        if not self.single and (0xf7 >= slave >= 0x00):
+            del self.__slaves[slave]
+        else: raise ParameterException('slave index out of range')
+
+    def __getitem__(self, slave):
+        ''' Used to get access to a slave context
+
         :param slave: The slave context to get
         :returns: The requested slave context
         '''

test/test_server_context.py

@@ -22,6 +22,12 @@ def testSingleContextGets(self):
         for id in xrange(0, 0xff):
             self.assertEqual(self.slave, self.context[id])
 
+    def testSingleContextDeletes(self):
+        ''' Test removing on multiple context '''
+        def _test():
+            del self.context[0x00]
+        self.assertRaises(ParameterException, _test)
+
     def testSingleContextIter(self):
         ''' Test iterating over a single context '''
         expected = (0, self.slave)
@@ -60,6 +66,11 @@ def testMultipleContextGets(self):
         for id in xrange(0, 10):
             self.assertEqual(self.slaves[id], self.context[id])
 
+    def testMultipleContextDeletes(self):
+        ''' Test removing on multiple context '''
+        del self.context[0x00]
+        self.assertRaises(ParameterException, lambda: self.context[0x00])
+
     def testMultipleContextIter(self):
         ''' Test iterating over multiple context '''
         for id, slave in self.context: