[Tutor] Why is an OrderedDict not sliceable?

[Albert-Jan Roskam]

> To: tutor at python.org
> From: alan.gauld at btinternet.com
> Date: Fri, 22 Jan 2016 00:12:18 +0000
> Subject: Re: [Tutor] Why is an OrderedDict not sliceable?
> 
> On 22/01/16 00:00, Steven D'Aprano wrote:
> 
> > Also, you have a problem -- what happens if the incomplete postcode is 
> > missing the first digit? (I suppose for that case, you just have to do a 
> > slow linear search.) 
If the postcode letters are missing, I look up the insertion point for the postcode digits. I then indeed use a linear search to loop through that postal code 4-digits area. Then I use the apartment number to filter out impossible street(s). Often postcodes for odd and even house numbers differ. So if, for instance, I have postcode digits 1234, no postcode letters, and apartment number 312, I can ignore all odd number ranges, and all ranges that do not include 312 (many streets have just a few dozen numbers). I then end up with a bunch of options, which I call candidates. Finally, I use difflib.SequenceMatcher to try and select a record of which the "dirty" street name, most closely resembles the standard street name in the list of candidates. I did not consider what to do when one postcode letter is missing, or when letters are transposed. I expect (and hope!) that the street/city cannot be derived and that this record needs to be reviewed manually. And in case you wondered: yes, it sucks that all these corrections need to be done "after the fact". A good reason to learn how to use Django or Flask to create a data entry screen and start with crisp clean data :-)
> Which is why a different solution may be better suited.
> What about an in-memory SQLite table? Then you can use
> a LIKE based select and let the library do the hard work.
Ouch, I considered marshall and pickle to cache the data, because running the query on MS SQL takes more time than I like. But I am embarrassed to say I did not even consider SQLite. I will reconsider this. Thank you! 
> Just a thought.
> 
> -- 
> Alan G
> Author of the Learn to Program web site
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