lib/logging: Set handlers as set instead of list

Handlers is currently initialized as empty list. The operation most per formed is __contains__. Set performs faster for this and ordering of handler is not a concern. Hence replace the list initialization with set.

Author: adityagesh

Lib/logging/__init__.py

@@ -1483,7 +1483,7 @@ def __init__(self, name, level=NOTSET):
         self.level = _checkLevel(level)
         self.parent = None
         self.propagate = True
-        self.handlers = []
+        self.handlers = set()
         self.disabled = False
         self._cache = {}
 
@@ -1685,7 +1685,7 @@ def addHandler(self, hdlr):
         """
         with _lock:
             if not (hdlr in self.handlers):
-                self.handlers.append(hdlr)
+                self.handlers.add(hdlr)
 
     def removeHandler(self, hdlr):
         """