Allow non-ascii labels in graph vertices (at least for plotting)

[kcrisman]

Apparently graph vertex labels have to be ASCII.

Graph({'Б':[1,2]}).plot()

See here and the duplicate here.

Component: graph theory

Author: Frédéric Chapoton

Branch: e6523a1

Reviewer: Jori Mäntysalo

Issue created by migration from https://trac.sagemath.org/ticket/21008

[fchapoton]

comment:1

Here is a tentative. Sometimes the character is not available in the usual font. At least
this works for the more common utf8 characters.

http://stackoverflow.com/questions/10960463/non-ascii-characters-in-matplotlib

---

New commits:

6b6633c

trac 21008 allow unicode labels in graphs

[fchapoton]

Branch: u/chapoton/21008

[fchapoton]

Author: Frédéric Chapoton

[fchapoton]

Commit: 6b6633c

[jm58660]

comment:2

Mäntysalo can review this patch made by Frédéric.

[jm58660]

Reviewer: Jori Mäntysalo

[kcrisman]

comment:3

I take it that would create some self-referential directed graph of review with Unicode vertices :-) just make sure it doesn't break any current graph plots!

[paulmasson]

comment:4

Documentation doesn't build with this fix. See #13161 for similar problem.

Also, the Russian character displays as a square box on Mac OS X El Capitan. Local Unicode fonts do not get incorporated into matplotlib output. Shouldn't there be some simple way to use local fonts?

[sagetrac-git]

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

7d03de3

trac 21008 utf8 encoding of file, plus nicer doctest

[sagetrac-git]

Changed commit from 6b6633c to 7d03de3

[jm58660]

comment:6

I don't understand. This works:

DiGraph({u'Mäntysalo':[u'Frédéric']}).plot()

but this does not:

D = DiGraph()
D.add_edge(u'Mäntysalo', u'Frédéric')
G.show()

[jm58660]

comment:7

Also src/sage/combinat/posets/posets.py fails some test.

[fchapoton]

comment:8

Replying to @jm58660:

I don't understand. This works:

DiGraph({u'Mäntysalo':[u'Frédéric']}).plot()

but this does not:

D = DiGraph()
D.add_edge(u'Mäntysalo', u'Frédéric')
G.show()

It should be D.show(), and it works for me.

[sagetrac-git]

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

e6523a1

trac 21008 fixing doctests in posets

[sagetrac-git]

Changed commit from 7d03de3 to e6523a1

[jm58660]

comment:11

My mistake. Now it works and also

D = DiGraph()
D.add_edge(u'Frédéric', 'review', u'Mäntysalo')
D.show(edge_labels=True)

works.

[kcrisman]

comment:12

Do we want all vertex labels to be unicode automatically? (I'm not sure if that is what is happening with the changed doctest in posets.)

[fchapoton]

comment:13

labels are converted to unicode in the plot, not in the graphs themselves.

[kcrisman]

comment:14

Got it, thanks.

[vbraun]

Changed branch from u/chapoton/21008 to e6523a1

[sagetrac-tmonteil]

comment:16

On my machine (7.4.beta1), the example given in the ticket description does not work:

sage: Graph({'Б':[1,2]}).plot()
...
UnicodeDecodeError: 'ascii' codec can't decode byte 0xd0 in position 0: ordinal not in range(128)

Probably due to:

sage: type('Б')
<type 'str'>
sage: type(u'Б')
<type 'unicode'>

[sagetrac-tmonteil]

Changed commit from e6523a1 to none

[fchapoton]

comment:17

you forgot the u. Ths is not an ascii string. As long as nobody cares about py3, we have to add a u for unicode strings.

[sagetrac-tmonteil]

comment:18

The point was that 'Б' is a valid string (through not unicode), which is not handled by plot. If it will automatically be fixed by Python 3, it is probably better not to add artificial noise into the source code.