Chris Withers writes:

Why and how are python tuples (like, this) handled differently (and not in a logical way I can see...) than python lists [like, this]? The "how" has been explained already.

The "why" is only my guess: support for the widespread idiom "<dict>.items()", "objectItems" etc. Form the DTML reference: sequence-key The key associated with the element in an items sequence. An items sequence is a sequence of value pairs that represent a mapping from a key to a value. Dieter