clean dense_graph.pyx

[dcoudert]

The big change in this ticket is to use yield in iterators instead of first building a list and then returning an iterator over that list. This should speed up methods using these iterators.

On the way, I have put try.. except TypeError around the 2 sorted operations.

We also do PEP8 cleaning.

[dcoudert]

New commits:

​56cd44f

trac #26567: clean dense_graph.pyx and use yield in iterators

[tscrim]

On the error messages, please remove the !.

I think a better way to do

                        try:
                            v, u = sorted((self.vertex_label(v_int),
                                           self.vertex_label(u_int)))
                        except TypeError:
                            v = self.vertex_label(v_int)
                            u = self.vertex_label(u_int)

is to do

                        v = self.vertex_label(v_int)
                        u = self.vertex_label(u_int)
                        try:
                            if u < v:
                                v, u = u, v
                        except TypeError:
                            pass

as it does not create an intermediary objects (the tuple and the resulting list), I would guess one comparison is faster than calling sorted, and we only change things if we need to.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​cbc0528	trac #26567: Merged with 8.5.beta1
​aadaf14	trac #26567: implement reviewers comments
​32e15a0	trac #26567: correct error

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​0433888

trac #26567: improvements

[dcoudert]

All comment's implemented.

[tscrim]

Thanks. I just want to wait for a green patchbot. Once one comes back (morally) green, we can set a positive review.

[tscrim]

The doctest failures seem unrelated.

[jhpalmieri]

Are there any plans for similar changes to sparse_graph.pyx, in particular to iterator_edges? I tried doing something similar, but it led to other problems, so it would be better if someone who knows the graph theory stuff better to do it. The code in sparse_graph.pyx leads to Python 3 doctest failures with simplicial complexes.