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Message: [QUOTE="Steven D'Aprano, post: 1828476"] Replying to myself... how sad. On reading it, that came across more snarky than I intended. Sorry. However, I wasn't completely insane, since I came across this tidbit: [URL]http://python.active-venture.com/ref/comparisons.html[/URL] "Mappings (dictionaries) compare equal if and only if their sorted (key, value) lists compare equal. Outcomes other than equality are resolved consistently, but are not otherwise defined." with a footnote leading to this comment: "Earlier versions of Python used lexicographic comparison of the sorted (key, value) lists, but this was very expensive for the common case of comparing for equality." I also suggested: I certainly can't prove it, since my example pseudo-code fails even on the example I used earlier. Sigh. In summary: Equality of dicts is guaranteed. Two dicts are equal if and only if their keys:value pairs are equal. Other orderings between dicts are calculated consistently but not in any documented way. One gotcha is that some dicts are unordered: py> {1:1j} < {1:2j} Traceback (most recent call last): File "<stdin>", line 1, in ? TypeError: cannot compare complex numbers using <, <=, >, >= but even that is special-cased up to the wazzoo: py> {1:1j} < {1:1j} False [/QUOTE]