[Tutor] Question about Dictionaries

Alan Gauld alan.gauld at btinternet.com
Tue Aug 17 01:20:43 CEST 2010

"Chorn, Guillaume" <guillaume_chorn at merck.com> wrote

> dictionary, but can I look up the key associated with a particular
> value?  

Not directly but its not hard to do bearing in mind you will 
get a collection back.:

>>> d = {1:10,2:20,3:10,4:20}
>>> val = 10
>>> ks = [k for k in d if d[k] == val]
>>> ks
[1, 3]

You need to trawl the dictionary whatever you do
(unless you get very sophisticated and build a double 
dictionary class, but then insertions get slow because 
you have to update both versions...)


Alan Gauld
Author of the Learn to Program web site

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