add count_listeners() method

eventemitter/__init__.py

@@ -1,4 +1,4 @@
-__version__ = "2.0"
+__version__ = "2.1"
 __author__ = "Rossen Georgiev"
 
 from collections import defaultdict, OrderedDict
@@ -155,4 +155,19 @@ def remove_all_listeners(self, event=None):
                 if event in self.__callbacks:
                     del self.__callbacks[event]
 
+    def count_listeners(self, event):
+        """
+        Returns a count of how many listeners are
+        registered registed for a specific event
+
+        :param event: event identifier
+        :returns: number of listeners
+        :rtype: int
+        """
+        if hasattr(self, '_EventEmitter__callbacks'):
+            if event in self.__callbacks:
+                return len(self.__callbacks[event])
+
+        return 0
+
 

tests/test_eventemitter.py

@@ -202,3 +202,25 @@ def aaa():
 
         self.idle()
         self.assertEqual(result, [3, 2, 1])
+
+    def test_count_listeners(self):
+        @self.dummy.on('event')
+        def func_one():
+            self.calls += 1
+
+        self.assertEqual(self.dummy.count_listeners('event'), 1)
+
+        self.dummy.once('event', func_one)
+
+        self.assertEqual(self.dummy.count_listeners('event'), 1)
+
+        self.dummy.remove_all_listeners('event')
+
+        self.assertEqual(self.dummy.count_listeners('event'), 0)
+
+    def test_count_listeners_with_no_listeners(self):
+        self.assertEqual(self.dummy.count_listeners(None), 0)
+        self.assertEqual(self.dummy.count_listeners('event'), 0)
+        self.assertEqual(self.dummy.count_listeners(''), 0)
+        self.assertEqual(self.dummy.count_listeners(1), 0)
+        self.assertEqual(self.dummy.count_listeners(0), 0)