Jim wrote: > I have an application that will maintain an in-memory database in the > form of a list of lists. Does anyone know of a way to search for and > retreive "records" from such a structure?
The answer very much depends on the manner in which you want to do the look-up. If you only need to do exact-match look-up for items with unique keys (e.g. find the single record where SSN=1234567890) then using a dictionary is by far the best solution. It's fast and it's easy. If you expect to do exact-match look-up where the keys are not unique then build a dictionary containing 'set' objects which are the sets of records which have the given key. This lets you neatly find the intersection of selections on multiple criteria (e.g. matches = zipcode_index["94101"] & hometype_index["condo"] ). If you need to do range matching (e.g. 20000 <= salary < 50000) then your best bet is to keep a list of the records sorted in the ordering of the key, do a binary search to find where the lower and upper bounds lie within the sorted list and then take a slice. If you also have some index dictionaries containing sets then you can combine these two methods with something like 'matches = set(salary_index[lo_sal:hi_sal]) & zipcode_index["81435"] ' Having said all that, if you think that there is any possibility that you might ever want to expand the functionality of your program to require either (a) more complex and flexible searching and/or (b) putting the database somewhere else, then I would strongly suggest that you use PySQLite. SQLite is an efficient in-memory database with an SQL engine and the Python interface conforms to the DB-API spec, so you won't need to change your code (much) if you want to move the database to some MySQL, Oracle, Sybase or DB2 server at a later date. Furthermore SQLite is included in Python 2.5 as standard. -- http://mail.python.org/mailman/listinfo/python-list
