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

25 Sep 2004

      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