> To my understanding, a slice isn't automatically a copy - it will be > in most cases, but there are cases where the bytecode compiler will > use the original list as an optimization. One example: > > >>> s = 'abc' > >>> t = s[:] > >>> s is t > True > > I'm willing to be corrected here, but my understanding was that for > loop iteration was one of those optimization cases.
It looks like it's an immutable-optimization from my further testing (strings being immutable): >>> a = [1,2,3] # use a list (mutable) >>> b = a[:] >>> a is b False >>> a = (1,2,3) # use a tuple (immutable) >>> b = a[:] >>> a is b True > necessary for code clarity - I would contend that: > > for x in intial_list[a:b]: > do stuff > > is easier to read than: > > sub_list = initial_list[a:b] > for x in sub_list: > do stuff in most cases, heartily agreed, so no contention here. >> Yes, it would be nice if this worked because it's logically >> true...except that it doesn't work (at least in Postgres and >> MS-SQL Server): > > Aw...crap. You are, of course, completely correct. I've been spending > too much time in MySQL of late, and I forgot that this was an > eccentricity of MySQL. It's just a shame it's not readily available in other SQL flavors, as it bugs me every time I need to add umpteen GROUP BY entries just so I can get some values for the SELECT clause. -tim --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Django developers" group. To post to this group, send email to django-developers@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/django-developers?hl=en -~----------~----~----~----~------~----~------~--~---
