On Friday, July 25, 2014 9:28:32 PM UTC-4, Steven D'Aprano wrote: > On Fri, 25 Jul 2014 17:06:17 -0700, Bruce Whealton wrote: Steven, See below please. The explanation did help. > > > OK, Eclipse with PyDev doesn't like this first line, with the function: > > > def add(self, (sub, pred, obj)): > > > > In Python 2, you could include parenthesised parameters inside function > declarations as above. That is effectively a short cut for this version, > where you collect a single argument and then expand it into three > variables: > > > > def add(self, sub_pred_obj): > > sub, pred, obj = sub_pred_obj > I setup Eclipse to use python 2.7.x and tried to run this and it just gave an error on line 9 where the def add function is declared. It just says invalid syntax and points at the parentheses that are in the function definition def add(self, (subj, pred, obj)): So, from what you said, and others, it seems like this should have worked but eclipse would not run it. I could try to load it into IDLE. > > > > In Python 3, that functionality was dropped and is no longer allowed. Now > you have to use the longer form. > I'm not sure I follow what the longer method is. Can you explain that more, please. > > > [...] > > > There are other places where I thought that there were too many > > > parentheses and I tried removing one set of them. For example this > > > snippet here: > > > > > > def remove(self, (sub, pred, obj)): > > > """ > > > Remove a triple pattern from the graph. """ > > > triples = list(self.triples((sub, pred, obj))) > > > > Firstly, the remove method expects to take a *single* argument (remember > > that self is automatically provided by Python) which is then automatically > > expanded into three variables sub, pred, obj. So you have to call it with a > > list or tuple of three items (or even a string of length exactly 3). >
> Then, having split this list or tuple into three items, it then joins them > > back again into a tuple: > > > > (sub, pred, obj) > passes that tuple to the triples method: > self.triples((sub, pred, obj)) > > > > (not shown, but presumably it uses the same parenthesised parameter trick), > > and then converts whatever triples returns into a list: > The full code listing should be available in the code paste link that I included. > > > list(self.triples((sub, pred, obj))) > > > > that list then being bound to the name "triples". > > Thanks, the explanation helped, Bruce -- https://mail.python.org/mailman/listinfo/python-list
