Christoph Zwerschke <[EMAIL PROTECTED]> wrote: ... > I have started the thread in the first place because I believed it is > pretty unabmiguous what an "ordered dictionary" is and how it should
I think you're wrong here. People in the past who have requested or implemented stuff they called 'ordered dicts' in the past had in mind drastically different things, based on some combination of insertion orders, keys, and _values_. So, ambiguity is definitely present in the phrase 'ordered dictionary', because there are so many different criteria whereby the 'ordering' could take place. Note the plural in 'insertion orderS': some people care about the FIRST time a key was added to a dict, some about the LAST time it was added, some about the latest time it was 'first inserted' (added and wasn't already there) as long as it's never been deleted since that occasion -- and these are just a few of the multifarious orders based on the time of insertions and deletions of keys. The number of variations is staggering, e.g., consider x['a'] = 1 x['b'] = 2 x['a'] = 1 in some applications you'd want to have 'b' come before 'a' because the last time of addition was earlier for 'b' -- but in others you might want 'a' first because the latest addition wasn't really one, since it didn't really change anything (because the value inserted was the same as the one already there -- it would be different, for those other apps, if the RHS of the third assignment was 0 rather than 1...). To get 'ordered dicts' into Python, you have to identify ONE unambiguous definition which has a large-enough number of use-cases, possibly customizable through some reasonably SIMPLE combination of flags and a callable or two, like the 'sorted' built-in has a 'reversed' flag and 'key' and 'cmp' optional callables. Expect a lot of flak from those who have been pining for an 'ordered dict' which does NOT match your one unambiguous definition...;-) If the field of use cases for 'ordered dicts' is just too fragmented, it's quite possible that it's best not to have any single kind built-in, even though, could all different use cases be combined (which by hypothesis is unfeasible), "critical mass" would be reached... Alex -- http://mail.python.org/mailman/listinfo/python-list
