On Tuesday, December 6, 2011 2:42:35 PM UTC+8, Rainer Grimm wrote: > Hello, > > > try: > > songs = [Song(id) for id in song_ids] > > except Song.DoesNotExist: > > print "unknown song id (%d)" % id > that's is a bad programming style. So it will be forbidden with python 3. The > reason is that list comprehension is a construct from the functional world. > It's only syntactic sugar for the functions map and filter. So functions have > to be pure functions. To say it in other words, they have to be side-effect > free. But the python construct from above pollutes the namespace with name id. > > Greetings from Rottenburg, > Rainer
The list might have to grow in a careless way that might lead to a crash in the for inside a list that can't be trapped for errors directly. -- http://mail.python.org/mailman/listinfo/python-list
