Unicode text in matplotlib plot gives error in ipython

Question

I am trying to plot unicode characters in a matplotlib plot in an ipython notebook.

# For example:
plt.title("α")

However, it gives a UnicodeEncodeError. I have tried importing the unicode_literals module as suggested in the matplotlib documentation here: http://matplotlib.org/examples/text_labels_and_annotations/unicode_demo.html. I have also tried using a unicode string with plt.title(u"α"), as suggested here: Unicode in ipython notebook.

Neither approach has affected the error output, (which I've put at the bottom).

How can I get unicode strings to plot in matplotlib in an ipython notebook?

I am not interested in using LaTeX in this case, if that is ok.

---------------------------------------------------------------------------
UnicodeEncodeError                        Traceback (most recent call last)
/usr/local/lib/python3.5/site-packages/IPython/core/formatters.py in __call__(self, obj)
    305                 pass
    306             else:
--> 307                 return printer(obj)
    308             # Finally look for special method names
    309             method = get_real_method(obj, self.print_method)

/usr/local/lib/python3.5/site-packages/IPython/core/pylabtools.py in <lambda>(fig)
    225 
    226     if 'png' in formats:
--> 227         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    228     if 'retina' in formats or 'png2x' in formats:
    229         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

/usr/local/lib/python3.5/site-packages/IPython/core/pylabtools.py in print_figure(fig, fmt, bbox_inches, **kwargs)
    117 
    118     bytes_io = BytesIO()
--> 119     fig.canvas.print_figure(bytes_io, **kw)
    120     data = bytes_io.getvalue()
    121     if fmt == 'svg':

/usr/local/lib/python3.5/site-packages/matplotlib/backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2178                     orientation=orientation,
   2179                     dryrun=True,
-> 2180                     **kwargs)
   2181                 renderer = self.figure._cachedRenderer
   2182                 bbox_inches = self.figure.get_tightbbox(renderer)

/usr/local/lib/python3.5/site-packages/matplotlib/backends/backend_agg.py in print_png(self, filename_or_obj, *args, **kwargs)
    525 
    526     def print_png(self, filename_or_obj, *args, **kwargs):
--> 527         FigureCanvasAgg.draw(self)
    528         renderer = self.get_renderer()
    529         original_dpi = renderer.dpi

/usr/local/lib/python3.5/site-packages/matplotlib/backends/backend_agg.py in draw(self)
    472 
    473         try:
--> 474             self.figure.draw(self.renderer)
    475         finally:
    476             RendererAgg.lock.release()

/usr/local/lib/python3.5/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     60     def draw_wrapper(artist, renderer, *args, **kwargs):
     61         before(artist, renderer)
---> 62         draw(artist, renderer, *args, **kwargs)
     63         after(artist, renderer)
     64 

/usr/local/lib/python3.5/site-packages/matplotlib/figure.py in draw(self, renderer)
   1157         dsu.sort(key=itemgetter(0))
   1158         for zorder, a, func, args in dsu:
-> 1159             func(*args)
   1160 
   1161         renderer.close_group('figure')

/usr/local/lib/python3.5/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     60     def draw_wrapper(artist, renderer, *args, **kwargs):
     61         before(artist, renderer)
---> 62         draw(artist, renderer, *args, **kwargs)
     63         after(artist, renderer)
     64 

/usr/local/lib/python3.5/site-packages/matplotlib/axes/_base.py in draw(self, renderer, inframe)
   2317 
   2318         for zorder, a in dsu:
-> 2319             a.draw(renderer)
   2320 
   2321         renderer.close_group('axes')

/usr/local/lib/python3.5/site-packages/matplotlib/artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     60     def draw_wrapper(artist, renderer, *args, **kwargs):
     61         before(artist, renderer)
---> 62         draw(artist, renderer, *args, **kwargs)
     63         after(artist, renderer)
     64 

/usr/local/lib/python3.5/site-packages/matplotlib/text.py in draw(self, renderer)
    747 
    748         with _wrap_text(self) as textobj:
--> 749             bbox, info, descent = textobj._get_layout(renderer)
    750             trans = textobj.get_transform()
    751 

/usr/local/lib/python3.5/site-packages/matplotlib/text.py in _get_layout(self, renderer)
    359                 w, h, d = renderer.get_text_width_height_descent(clean_line,
    360                                                         self._fontproperties,
--> 361                                                         ismath=ismath)
    362             else:
    363                 w, h, d = 0, 0, 0

/usr/local/lib/python3.5/site-packages/matplotlib/backends/backend_agg.py in get_text_width_height_descent(self, s, prop, ismath)
    227             fontsize = prop.get_size_in_points()
    228             w, h, d = texmanager.get_text_width_height_descent(s, fontsize,
--> 229                                                                renderer=self)
    230             return w, h, d
    231 

/usr/local/lib/python3.5/site-packages/matplotlib/texmanager.py in get_text_width_height_descent(self, tex, fontsize, renderer)
    673         else:
    674             # use dviread. It sometimes returns a wrong descent.
--> 675             dvifile = self.make_dvi(tex, fontsize)
    676             dvi = dviread.Dvi(dvifile, 72 * dpi_fraction)
    677             try:

/usr/local/lib/python3.5/site-packages/matplotlib/texmanager.py in make_dvi(self, tex, fontsize)
    397 
    398         if DEBUG or not os.path.exists(dvifile):
--> 399             texfile = self.make_tex(tex, fontsize)
    400             outfile = basefile + '.output'
    401             command = self._get_shell_cmd(

/usr/local/lib/python3.5/site-packages/matplotlib/texmanager.py in make_tex(self, tex, fontsize)
    312             else:
    313                 try:
--> 314                     fh.write(s.encode('ascii'))
    315                 except UnicodeEncodeError as err:
    316                     mpl.verbose.report("You are using unicode and latex, but "

UnicodeEncodeError: 'ascii' codec can't encode character '\xb0' in position 289: ordinal not in range(128)

For me plt.title("α") works fine when using unicode_literals. Omitting the future import, plt.title(u"α") works as well. So I guess you need to provide a minimal reproducible example of the issue. Especially it seems that the traceback goes along some latex rendering in texmanager.py, which suggests you are actually using Latex. This could of course be a problem together with unicode characters. — ImportanceOfBeingErnest
– ImportanceOfBeingErnest, Commented Feb 21, 2017 at 8:24

Community · Accepted Answer · 2017-05-23 10:29:49Z

1

Thanks for the help amoose136. But I managed to figure it out. There were two things.

First, I was using TeX to do the text:

matplotlib.rc('text', usetex=True)

TeX and unicode don't mix.

Omitting this line allowed the matplotlib documentation example to work (in the question info).

Secondly, it then compiled, but I had my (greek) characters showing up as boxes. To fix this, I followed the advice here: Non-ASCII characters in Matplotlib, and used a font that supported my characters, like Arial:

matplotlib.rc('font', family='Arial')

Hope this helps anyone!

edited May 23, 2017 at 10:29

CommunityBot

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answered Feb 22, 2017 at 9:34

mathematica_noob

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Comments

amoose136 · Accepted Answer · 2017-02-21 17:33:32Z

0

Without a full example it's difficult to say for sure what's going on but I can tell you what I did when I had a similar issue and I wanted it to run on both python 2 and python 3 for future proofing.

In the header of the file:

#!/usr/bin/env python
# coding: utf-8
import six,sys
# needed for utf-encoding on python 2:
if six.PY2:
    reload(sys)
    sys.setdefaultencoding('utf8')

Note that for a good reason specified by the pep-0263 standard, the # coding: utf-8 line is actually important and does something. Try that and see if if fixes it. If not, provide a complete example and I will update this answer accordingly.

Alternatively, try changing it to plt.title(u'α').

answered Feb 21, 2017 at 17:33

amoose136

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