--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/python/example/mutable_defaults.py	Thu Oct 23 15:29:48 2014 -0700
@@ -0,0 +1,15 @@
+#!/usr/bin/env python
+
+# see also: http://www.daniweb.com/software-development/python/threads/66697
+
+class Foo(object):
+  def __init__(self, mutable=['default']):
+    self.foo = mutable
+    self.foo.append(1)
+
+if __name__ == '__main__':
+  bar = Foo()
+  print len(bar.foo)
+  fleem = Foo()
+  print len(fleem.foo)
+  assert len(fleem.foo) == 2, "Don't use default mutable arguments!"