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I'm trying to get mathtext to render my figure axes labels correctly (ideally I don't want to use Latex itself to render the text). However, this small minimum working example produces the error shown below. It seems to me that it should work, is maybe a necessary package not installed?

I'm running matplotlib 2.2.2 and Python 3.5

import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(1,1,1)
ax.plot(0,0)
ax.set_ylabel(r'$\mathrm A$')

the error produced:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/mathtext.py", line 2516, in parse
    result = self._expression.parseString(s)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1632, in parseString
    raise exc
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1622, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3395, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3919, in parseImpl
    return super(ZeroOrMore, self).parseImpl(instring, loc, doActions)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3848, in parseImpl
    loc, tokens = self_expr_parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3378, in parseImpl
    loc, resultlist = self.exprs[0]._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1405, in _parseNoCache
    tokens = fn( instring, tokensStart, retTokens )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1049, in wrapper
    ret = func(*args[limit[0]:])
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/mathtext.py", line 2585, in math_string
    return self._math_expression.parseString(toks[0][1:-1])
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1632, in parseString
    raise exc
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1622, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3848, in parseImpl
    loc, tokens = self_expr_parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3717, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1379, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 3530, in parseImpl
    ret = e._parse( instring, loc, doActions )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1529, in _parseCache
    value = self._parseNoCache(instring, loc, doActions, callPreParse)
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1405, in _parseNoCache
    tokens = fn( instring, tokensStart, retTokens )
  File "/usr/local/lib/python3.5/dist-packages/pyparsing.py", line 1049, in wrapper
    ret = func(*args[limit[0]:])
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/mathtext.py", line 2687, in unknown_symbol
    raise ParseFatalException(s, loc, "Unknown symbol: %s" % c)
pyparsing.ParseFatalException: Unknown symbol: \mathrm (at char 0), (line:1, col:1)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/backends/backend_gtk3agg.py", line 39, in on_draw_event
    self._render_figure(w, h)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/backends/backend_gtk3agg.py", line 30, in _render_figure
    backend_agg.FigureCanvasAgg.draw(self)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/backends/backend_agg.py", line 433, in draw
    self.figure.draw(self.renderer)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/figure.py", line 1475, in draw
    renderer, self, artists, self.suppressComposite)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/image.py", line 141, in _draw_list_compositing_images
    a.draw(renderer)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/axes/_base.py", line 2607, in draw
    mimage._draw_list_compositing_images(renderer, self, artists)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/image.py", line 141, in _draw_list_compositing_images
    a.draw(renderer)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/axis.py", line 1204, in draw
    self.label.draw(renderer)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/artist.py", line 55, in draw_wrapper
    return draw(artist, renderer, *args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/text.py", line 706, in draw
    bbox, info, descent = textobj._get_layout(renderer)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/text.py", line 309, in _get_layout
    ismath=ismath)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/backends/backend_agg.py", line 237, in get_text_width_height_descent
    self.mathtext_parser.parse(s, self.dpi, prop)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/mathtext.py", line 3294, in parse
    box = self._parser.parse(s, font_output, fontsize, dpi)
  File "/usr/local/lib/python3.5/dist-packages/matplotlib/mathtext.py", line 2522, in parse
    six.text_type(err)]))
ValueError: 
\mathrm A
^
Unknown symbol: \mathrm (at char 0), (line:1, col:1)

If you suspect this is an IPython bug, please report it at:
    https://github.com/ipython/ipython/issues
or send an email to the mailing list at [email protected]

You can print a more detailed traceback right now with "%tb", or use "%debug"
to interactively debug it.

Extra-detailed tracebacks for bug-reporting purposes can be enabled via:
    %config Application.verbose_crash=True
Improve this question
4
  • Do you mean \mathrm{A}? Commented Apr 12, 2018 at 10:06
  • I can't believe that that was the error... I feel a bit stupid :) You should make that as an answer so that I can accept it Commented Apr 12, 2018 at 10:22
  • Nah, this is close to a typo and the question should be closed for that very same reason. Commented Apr 12, 2018 at 10:24
  • 1
    Yes and no. In Latex itself you don't necessarily need the curly brakets. It would work without them Commented Apr 12, 2018 at 10:33

1 Answer 1

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1

You are correct that in LaTeX, \mathrm A is valid, but don't forget that the Matplotlib parser is not the same as LaTeX.

I tried this on Python 3.6.4 and Matplotlib 2.2.2, and the error no longer exists.

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