"Frank Millman" <fr...@chagford.com> wrote in message news:ld4ocf$9rg$1...@ger.gmane.org... > > "Chris Angelico" <ros...@gmail.com> wrote in message > news:captjjmqdusdfc1elbu6lf5-up__lae-63ii0uuvaggnem9u...@mail.gmail.com... >> On Sat, Feb 8, 2014 at 6:06 PM, Igor Korot <ikoro...@gmail.com> wrote: >>>>>> sorted(a.items(), key=a.get) >>> [('1', datetime.datetime(2012, 12, 28, 12, 15, 30, 100)), ('3', >>> datetime.datetim >>> e(2012, 12, 28, 12, 16, 44, 100)), ('2', datetime.datetime(2012, 12, 28, >>> 12, 17, >>> 29, 100))] > > That seemed like a neat trick, so I thought I would try to understand it a > bit better in case I could use it some day. > > I am using python3. I don't know if that makes a difference, but I cannot > get it to work. > >>>> d = {1: 'abc', 2: 'xyz', 3: 'pqr'} >>>> sorted(d.items(), key=d.get) > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: unorderable types: NoneType() < NoneType() >>>> > > I know that python3 is stricter regarding ordering of non-comparable > types, but I don't see where None is coming from. > > I have python 2.7.3 on another machine. Here are the results - > >>>> d = {1: 'abc', 2: 'xyz', 3: 'pqr'} >>>> sorted(d.items(), key=d.get) > [(1, 'abc'), (2, 'xyz'), (3, 'pqr')] > > It did not crash, but it did not sort. > > Then I changed the keys to strings, to match Igor's example - > >>>> d = {'1': 'abc', '2': 'xyz', '3': 'pqr'} >>>> sorted(d.items(), key=d.get) > [('1', 'abc'), ('3', 'pqr'), ('2', 'xyz')] > > It works - now I am even more confused. >
As Chris replied in another post - > The problem here is actually your key function. my_dict.items() > returns a series of two-item tuples, none of which exists in your > dictionary; so you're actually sorting [None, None, None], which isn't > very useful. > > Try this: > > sorted_items = sorted(my_dict.keys(), key=my_dict.get) > for key in sorted_items: > print my_dict[key], key > Without realising it, you have answered all my questions - thanks very much. Frank -- https://mail.python.org/mailman/listinfo/python-list
