writing diagram to SVG uses ascii by default, not utf-8

Question

Pretty sure this is a question where I'm missing something simple/basic.

I recently upgraded pydrake to 1.32. When exporting the Diagram to SVG, it marks deprecated ports with the tombstone emoji, '\U0001faa6' . Something in the pydot pipeline is choosing to use ascii instead of unicode, and it's crashing my script.

Here's the offending line:

pydot.graph_from_dot_data(diagram.GetGraphvizString())[0].create_svg("diagram.svg")

I'm getting this UnicodeEncodeError:

'ascii' codec can't encode character '\U0001faa6' in position 1087: ordinal not in range(128)
  File [redacted], line 114, in make_diagram
    pydot.graph_from_dot_data(diagram.GetGraphvizString())[0].create_svg("diagram.svg")
  File [redacted], line 188, in <module>
    diagram, diagram_context, loggers = make_diagram()
                                        ^^^^^^^^^^^^^^
UnicodeEncodeError: 'ascii' codec can't encode character '\U0001faa6' in position 1087: ordinal not in range(128)

I've looked around to see if pydot has arguments where I can ask it to use unicode instead of ascii, but wasn't able to find anything.

I'm on Mac OS Sonoma 14.5. I've seen the tombstones appear previously on my linux machine, but not on my Mac, so I suspected it was something with my install. I updated pydot,graphviz on pip , but that hasn't fixed the problem.

Other stackoverflow posts I looked at:

• Graphviz not supporting UTF-8 encoding: this seems to work for svg but not png for them

• Cannot use utf-8 encoded image filename in order to customize node shape, also couldn't find a way to tell graphviz to use unicode

Answer 1

Running the following code

from pydrake.all import MultibodyPlant
import pydot

plant = MultibodyPlant(0.0)
plant.Finalize()

pydot.graph_from_dot_data(plant.GetGraphvizString())[0].write_svg("test.svg")

• linux, Drake master branch, pydot v2.0.0: works fine. I see the warning and the tombstones.
• mac, Drake v1.32.0, pydot v3.0.1: works fine. I see the warning and the tombstones.

Answer 2

The following "raw" Graphviz code & the svg:cairo driver produce the desired result. Note the different encoding.
dot -T svg:cairo myFile.gv >myFile.svg

digraph U {

/******************************************************************
see also:
https://forum.graphviz.org/t/how-to-enter-certain-utf-8-characters/1352/2
******************************************************************/
  test  [label=<&#x01faa6;>]
}