Iterating Over Dictionary From Arbitrary Location

Diez B. Roggisch deets at
Sat Jun 6 11:53:54 EDT 2009

akindo schrieb:
> Hi all. I am new to Python and have a problem regarding data structures.
> In my application I will be having several messages and my own type of 
> IDs (Lamport clocks) to go with these messages. I will need to 
> frequently ask for specific messages based on the ID. Hence a dictionary 
> seems a better choice than a list, as I will be using my own IDs to 
> index into the data structure. However, the problem is that I will also 
> at times ask for a specific message based on the ID key, but then want 
> _all_ messages with a higher ID returned as well. :shock: From my 
> research, there are two problems with a dictionary then: 1. it can't be 
> sorted (only returns a sorted list), 2. even if it was possible to sort 
> a dictionary, it is not possible to iterate over it from a given location.
> So, it seems I want the best of both worlds: specific indexing using my 
> own IDs/keys (not just by list element location), sorting and the 
> ability to start iterating from a specific location. I am trying to 
> prevent having to scan through a list from the beginning to find the 
> desired ID, and then return all elements after that. Is there another 
> data structure or design pattern which will do what I want? Thanks a lot 
> for any help! :)

you could use a list which is sorted and then use the bisect-module to 
look up your keys in O(log n). You could also map keys to list-indices.


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