On Wednesday, October 12, 2016 at 9:01:51 AM UTC-5, Daniel Krenn wrote:
> On 2016-10-12 13:39, Jori Mäntysalo wrote: 
> > More about this: In posets.py there is 
> > 
> >     try: 
> >         elements = D.topological_sort() 
> >     except Exception: 
> >         raise ValueError("Hasse diagram contains cycles.") 
> > 
> > and that should be "except TypeError", as that is what 
> > .topological_sort() raises from DiGraph that is not acyclic. 
> > 
> > But should a function without parameters like foo.bar() ever raise 
> > TypeError? If we can run that, then the object foo is of the right type 
> > and has bar()-function. Or where goes the limit between TypeError and 
> > ValueError, i.e. what we mean by 'type' -- is DAG a "type" or just a 
> > DiGraph with some special properties? 
> There could be a ContainsCycleError which has RuntimeError as a base... 

IMO a ValueError is better than a TypeError because topological_sort 
(implicitly) takes the DiGraph as an input, and the input type is correct, 
just its value is wrong. Although this is more towards bikeshedding...


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