forcing dictionary order

[Steven D. Majewski]

On Thu, 29 Mar 2001, Bob van der Poel wrote:

> 
> I'd like (not a must!) to walk a dictionary in the same order in which
> it was created. Example:
> 
> 	foo={ key1: (), key2: (), key3: () }
> 
> If I do:
> 	
> 	for a in foo.keys(): ...
> 
> the order is not "key1, key2, key3", which is what I want. Note, I can't
> do something simple like sort() on the keys since the are not in any
> alphanumeric order. I'm just using this to generate a largish table for
> another program, and the actual order doesn't matter for it to work
> properly, but it would nicer if it were in the correct logical order.
> So, I'm not going to spend a lot of time on this, but if there is a
> simple way????

Once they are in the dictionary, they keys are hashed, so any info
on the order of insertion is lost. 

You can create a Class based on UserDict, and override the __setitem__
method (and to be consistent, __delitem__ and update) to keep an ordered
list of keys in parallel. 

You might also redefine popitem to return pairs in the proper order. 
( Do you want FIFO or LIFO ? ) 

-- Steve Majewski