[Jeremy Hylton] > What's a sequence then? If you say anything that PySequence_Check() > says okay for, then there is almost no code that accepts a sequence. ? Isn't that backwards? PySequence_Check() says "yes" to every instance, and in 2.2 even says "yes" to dictionaries too (because Guido filled in PyDict_Type's tp_as_sequence slot in order to get at sq_contains).