8000 Long node names get mangled by `create_dot` · Issue #483 · pydot/pydot · GitHub
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Peiffap opened this issue May 30, 2025 · 2 comments · May be fixed by #486
Open

Long node names get mangled by create_dot #483

Peiffap opened this issue May 30, 2025 · 2 comments · May be fixed by #486

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@Peiffap
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Peiffap commented May 30, 2025 •
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Originally reported by @dougthor42 in networkx/networkx#7648.

When working with long node names (~ >130 characters), create_dot mangles the name by adding line breaks. This makes it hard to round-trip pydot.Graph objects through the dot command and read them back in again (which is what nx.nx_pydot.pydot_layout does).

A minimum reproduction is

>>> import networkx as nx
>>> import pydot
>>> import locale
>>> G = nx.Graph()
>>> G.add_node("=10chars= " * 14)
>>> P = nx.nx_pydot.to_pydot(G)
>>> bytes = P.create_dot()
>>> D = str(bytes, encoding=locale.getpreferredencoding())
>>> Q = pydot.graph_from_dot_data(D)[0]
>>> print(Q.get_nodes()[-1].get_name())
"=10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =\
10chars= "
>>> print(pydot.quote_id_if_necessary(str(list(G.nodes())[0])))
"=10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= =10chars= "

The two names aren't equal, and it would be nice if they were.
@Peiffap Peiffap mentioned this issue May 30, 2025
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@lkk7
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lkk7 commented Jun 1, 2025

(Continuing the discussion from #420)
(BTW, that PR doesn't fix the issue)

It's Graphviz (dot) itself that performs the name splitting, not pydot.

I couldn't find any documentation mentioning this. If this is an old, deeply ingrained thing, then they'll never change it. I understand it's probably for visual clarity, but still... 😞

I'm wondering what's the expected behavior of pydot in this situation.

I don't think we should:

  • Remove the split when reading an already split graph (because someone might be doing it intentionally)
  • Do that split anywhere in the internal representation (because it's undocumented, weird, and unexpected)

The least invasive way to fix the problem might be to extend get_node so that it also checks the "unsplit" names of existing nodes.

CC: @ferdnyc

@lkk7 lkk7 linked a pull request Jun 1, 2025 that will close this issue
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@lkk7
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lkk7 commented Jun 1, 2025

Proposed fix: #486
(tired of mypy complaining, but ignore that because everything else passes)

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Long names fix pydot/pydot
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@lkk7 @Peiffap
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