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Where has _circle_embedding gone?

asked 2018-11-27 09:59:33 +0200

Gordon gravatar image

updated 2020-01-12 13:32:50 +0200

FrédéricC gravatar image

After nearly killing myself (in frustration) installing Sage 8.4 from source on OSX 10.14.1 (Mojave), I discover that a graph plotting command that I frequently use has vanished, breaking a number of my own programs.

Previously (on SageMath up to 8.2) I would do

from sage.graphs.graph_plot import _circle_embedding

in order to access this.

Now I just get

ImportError: cannot import name _circle_embedding

I can relatively easily replace this particular function myself, but if it were something more complicated, I would be at a loss to know how to track down the cause for its disappearance and figure out how to get it back.

So I guess the questions are: has it only vanished for me due to a botched or incomplete installation, or has it somehow been removed from Sage? In either case, how can I recover it?

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answered 2018-11-27 11:55:00 +0200

slelievre gravatar image

In such a case you can inspect the source code repository, which is under version control.

One way to do that is at GitHub, where a copy of the version controlled repository exists.

Since the import was

from sage.graphs.graph_plot import _circle_embedding

one can visit

and see the file

The "History" button reveals commits that changed this file.

The last of those is "trac #22050: move methods to and update usage" and by clicking it you can see how the usage of _circle_embedding has evolved.

In particular, _circle_embedding is now a method you can apply to any graph directly without a need to import it.

For example, instead of doing:

sage: g = Graph('HKN?Yeb')
sage: from sage.graphs.graph_plot import _circle_embedding
sage: _circle_embedding(g, [1, 2, 4, 3, 0, 5])

the usage is now more direct, without import:

sage: g = Graph('HKN?Yeb')
sage: g._circle_embedding([1, 2, 4, 3, 0, 5])

Note that functions or methods starting with a single underscore _ are "private methods" and there is not much guarantee on them, including that they will still exist, or stay the same, or stay in the same place.

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A perfect answer I think, covering exactly what I needed to know. Awesome.

Gordon gravatar imageGordon ( 2018-11-27 12:33:41 +0200 )edit

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Asked: 2018-11-27 09:59:33 +0200

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Last updated: Nov 27 '18