Issue #25011: rlcomplete now omits private and special attribute names unless
the prefix starts with underscores.
diff --git a/Lib/rlcompleter.py b/Lib/rlcompleter.py
index 568cf36..613848f 100644
--- a/Lib/rlcompleter.py
+++ b/Lib/rlcompleter.py
@@ -142,20 +142,35 @@
             return []
 
         # get the content of the object, except __builtins__
-        words = dir(thisobject)
-        if "__builtins__" in words:
-            words.remove("__builtins__")
+        words = set(dir(thisobject))
+        words.discard("__builtins__")
 
         if hasattr(thisobject, '__class__'):
-            words.append('__class__')
-            words.extend(get_class_members(thisobject.__class__))
+            words.add('__class__')
+            words.update(get_class_members(thisobject.__class__))
         matches = []
         n = len(attr)
-        for word in words:
-            if word[:n] == attr and hasattr(thisobject, word):
-                val = getattr(thisobject, word)
-                word = self._callable_postfix(val, "%s.%s" % (expr, word))
-                matches.append(word)
+        if attr == '':
+            noprefix = '_'
+        elif attr == '_':
+            noprefix = '__'
+        else:
+            noprefix = None
+        while True:
+            for word in words:
+                if (word[:n] == attr and
+                    not (noprefix and word[:n+1] == noprefix) and
+                    hasattr(thisobject, word)):
+                    val = getattr(thisobject, word)
+                    word = self._callable_postfix(val, "%s.%s" % (expr, word))
+                    matches.append(word)
+            if matches or not noprefix:
+                break
+            if noprefix == '_':
+                noprefix = '__'
+            else:
+                noprefix = None
+        matches.sort()
         return matches
 
 def get_class_members(klass):