Duh. cmdqueue should be an instance variable, not a class variable.

gvanrossum · gvanrossum · commit 87fec22476ad · 2003-01-13T21:18:54.000Z
This was introduced in 1998 in rev. 1.13, where I imported extensive
patches that, I am sad to say, I didn't review as carefully as I
should have.
diff --git a/Lib/cmd.py b/Lib/cmd.py
@@ -68,7 +68,6 @@ class Cmd:
     identchars = IDENTCHARS
     ruler = '='
     lastcmd = ''
-    cmdqueue = []
     intro = None
     doc_leader = ""
     doc_header = "Documented commands (type help <topic>):"
@@ -86,6 +85,7 @@ def __init__(self, completekey='tab'):
         automatically.
 
         """
+        self.cmdqueue = []
         if completekey:
             try:
                 import readline
