[Zope] Re: Intersection/Union of ZCatalog result sets

[Max M]

Jonathan Hobbs wrote:

>>should run them through a "unique" routine -- there was a good one in the
>>CMFCalendar.CalendarTool.py routines, which I extracted and put into a
>>Python script in CalendarX.
>>
>>Here's the code, in its entirety:
>># Unique the results of a query (query)
>>results = []
>>rids = []
>>for item in query:
>>     rid = item.getRID()
>>     if not rid in rids:
>>         results.append(item)
>>         rids.append(rid)


That is about the worst way to implement a unique routine. As "rids" 
grow, you get a O^2 time.

Using a dict is much faster, at least for larger result sets.

unique = {}
for item in query:
      unique[item.getRID()] = item
return unique.values()

You could probably even do it as:

unique = {}
for item in query:
      unique[item] = None
return unique.keys()

But that depends on whether the objects are hashable.

-- 

hilsen/regards Max M, Denmark

http://www.mxm.dk/
IT's Mad Science