Why are there no ordered dictionaries?

Christoph Zwerschke cito at online.de
Mon Nov 21 02:02:36 CET 2005


Ben Finney wrote:

> Without an example, it's hard to know what you want to do and whether
> an ordered dictionary is the best way to do it.

I have indicated an example, discussed in more detail in another subthread.

>> There are already enough competing implementations.
> Have they been sufficiently shaken out to show a clearly superior
> version? Is any version sufficiently beneficial to write a PEP for its
> inclusion in the standard library?

At least it shows I'm not the only one who thinks ordered dictionaries 
may be sometimes nice to have.

 >> I simply wanted to ask why it is not available in the standard lib, 
 >> since I simply don't know
 >> - has it not been demanded loud enough?
> Loud demands don't count for much. PEPs with popular working
> implementations do.

Sorry, I did not mean "loud enough" but "often enough". The same what 
you are calling "popular."

>> - because nobody presented a satisfying implementation yet?
> I'm not sure what you mean by "satisfying".

You can take your own definition: "sufficiently shaken out", "working", 
"popular", and "succifiently beneficial" and "proven (to the BDFL's 
criteria)".

> Another possibility: ordered dictionaries are not needed when Python
> 2.4 has the 'sorted' builtin.

The 'sorted' function does not help in the case I have indicated, where 
"I do not want the keys to be sorted alphabetically, but according to 
some criteria which cannot be derived from the keys themselves."

-- Christoph



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