#15278: Hash and equality for graphs
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Reporter: SimonKing | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.13
Component: graph theory | Resolution:
Keywords: | Merged in:
Authors: Simon King | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/SimonKing/ticket/15278 | 07bad466ab9a3e2ffe82c142cc6d0c515f1ae452
Dependencies: #12601, #15491 | Stopgaps:
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Comment (by ncohen):
> A different question: Shall we simply rely on the error that is raised
by the static backend (which is an `AttributeError` when adding or
deleting a vertex and a `NotImplementedError` when adding ), or should we
catch the error and raise a `TypeError` instead, with an error message
telling that this is an immutable graph and adding a vertex is a bad idea
in the case of an immutable graph?
Hmmm.. Well, in the code of `static_sparse_backend` there is an add_vertex
function which whose code is the following :
{{{
raise ValueError("Thou shalt not add a vertex to an immutable graph")
}}}
But somehow this is not the exception that appears first when you add a
vertex from the Python object. Well, I agree with you that having an
exception saying that "this graph is immutable, and that's probably the
origin of your problem" would be cool. If would be prettier if those
exceptions were in the backend, and if these exceptions did appear when
calling the add_edge/vertex methods from the Python object though `:-)`
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/15278#comment:31>
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