Just ignore the above post. I am able to get it working for adding new artist with albums. But I am still getting some problems while updating the albums's sales values from Turogears/toscawidgets2 interface. Let me bring the problem to sqlalchemy level then I will post it further (if the problem still remains). The code in the above post is working fine for adding new Artist and Albums. Thanks Michael for helping me out.
On Tuesday, 7 August 2012 11:19:54 UTC+5:30, jeetu wrote: > > Thanks Michael for looking into my problem. I tried following your advice > but still not able to get the total_sale. Do I have to implement some > special getter/setter for memoized property. If you run the code, you will > see that nowhere 'print "SETTING TOTAL_SALES"' is getting executed which > is in the memoized definition. Also how can i access the memoized property > as it is not available in straight forward querying on Artist. > > http://pastebin.com/Gqa7b0dd > > On Tuesday, 7 August 2012 00:14:07 UTC+5:30, Michael Bayer wrote: >> >> @memoized_property is a handy tool, and works simply, just clear out >> __dict__ of that key and it's reset. >> >> since you're looking to work in python, the total sales are just: >> >> @memoized_property >> def total_sales(self): >> # This should be the sum of all Album sales for this Artist. It >> should >> # be updated as soon as/just after a new Album is added or an >> Album's >> # sales is updated. >> return sum([album.sales or 0 for album in self.albums]) >> >> the events you need are simple, just whenever "sales" or "artist" >> (ideally you'd name this in the singular since it is many-to-one) change, >> pop the "total_sales" out of the dict: >> >> from sqlalchemy.orm import validates >> >> class Album(Base): >> # ... >> @validates("sales") >> def _update_sales(self, key, value): >> if self.artist is not None: >> self.artist.__dict__.pop('total_sales', None) >> return value >> >> @validates("artist", include_removes=True) >> def _update_artist(self, key, artist, is_remove): >> artist.__dict__.pop('total_sales', None) >> return artist >> >> >> >> On Aug 6, 2012, at 4:08 AM, jeetu wrote: >> >> My problem scenario is analogous to the following. I have an Artist table >> and an Album table. Each artist can have multiple albums with sales of each >> album. The artist also has a total_sales column which is basically a >> cumulative of album's sales for that artist. I tried reading about >> attribute events and memoized property but I am unable to get it integrated >> with my code. I tried to achieve something like >> https://groups.google.com/forum/?fromgroups#!topic/sqlalchemy/o_KxuHwz4WQ. >> But my lack of thorough understanding of decoraters and sqlalchemy is >> proving to be a hindrance. My example code (heavily borrowed from resources >> on internet and sqlalchemy group) is http://pastebin.com/vhRTcrWV >> Just for information if at all it matters:n my actual code I am using >> toscawidgets (inside turbogears) and dynamic forms for creating Albums >> table's values and Artist's values on a single page. >> >> PS: I hope it is not sounding like homework >> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sqlalchemy" group. >> To view this discussion on the web visit >> https://groups.google.com/d/msg/sqlalchemy/-/CcGMUZ2UHSYJ. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]. >> For more options, visit this group at >> http://groups.google.com/group/sqlalchemy?hl=en. >> >> >> -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To view this discussion on the web visit https://groups.google.com/d/msg/sqlalchemy/-/ITKNMZrbeXEJ. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
