René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Unicode symbols encoded with `\\u....` with mathtext raise ParseFatalException","articleBody":"### Bug summary\n\nThe [documentation](https://matplotlib.org/stable/users/explain/text/mathtext.html#symbols) states that symbols can be encoded in mathtext with the following example:\n```python\nr'$\\u23ce$'\n```\nBut this does not work and raises a ParseFatalException.\n\n### Code for reproduction\n\n```Python\nimport matplotlib.pyplot as plt\nplt.title(r'$\\u23ce$')\nplt.show()\n```\n\n### Actual outcome\n\n```\nTraceback (most recent call last):\n  File \"/usr/lib/python3.13/site-packages/matplotlib/backends/backend_qt.py\", line 522, in _draw_idle\n    self.draw()\n    ~~~~~~~~~^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/backends/backend_agg.py\", line 382, in draw\n    self.figure.draw(self.renderer)\n    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/artist.py\", line 94, in draw_wrapper\n    result = draw(artist, renderer, *args, **kwargs)\n  File \"/usr/lib/python3.13/site-packages/matplotlib/artist.py\", line 71, in draw_wrapper\n    return draw(artist, renderer)\n  File \"/usr/lib/python3.13/site-packages/matplotlib/figure.py\", line 3257, in draw\n    mimage._draw_list_compositing_images(\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^\n        renderer, self, artists, self.suppressComposite)\n        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/image.py\", line 134, in _draw_list_compositing_images\n    a.draw(renderer)\n    ~~~~~~^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/artist.py\", line 71, in draw_wrapper\n    return draw(artist, renderer)\n  File \"/usr/lib/python3.13/site-packages/matplotlib/axes/_base.py\", line 3190, in draw\n    self._update_title_position(renderer)\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/axes/_base.py\", line 3144, in _update_title_position\n    if title.get_window_extent(renderer).ymin \u003c top:\n       ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/text.py\", line 969, in get_window_extent\n    bbox, info, descent = self._get_layout(self._renderer)\n                          ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/text.py\", line 382, in _get_layout\n    w, h, d = _get_text_metrics_with_cache(\n              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^\n        renderer, clean_line, self._fontproperties,\n        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n        ismath=ismath, dpi=self.get_figure(root=True).dpi)\n        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/text.py\", line 69, in _get_text_metrics_with_cache\n    return _get_text_metrics_with_cache_impl(\n        weakref.ref(renderer), text, fontprop.copy(), ismath, dpi)\n  File \"/usr/lib/python3.13/site-packages/matplotlib/text.py\", line 77, in _get_text_metrics_with_cache_impl\n    return renderer_ref().get_text_width_height_descent(text, fontprop, ismath)\n           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/backends/backend_agg.py\", line 215, in get_text_width_height_descent\n    self.mathtext_parser.parse(s, self.dpi, prop)\n    ~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/mathtext.py\", line 86, in parse\n    return self._parse_cached(s, dpi, prop, antialiased, load_glyph_flags)\n           ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"/usr/lib/python3.13/site-packages/matplotlib/mathtext.py\", line 100, in _parse_cached\n    box = self._parser.parse(s, fontset, fontsize, dpi)\n  File \"/usr/lib/python3.13/site-packages/matplotlib/_mathtext.py\", line 2173, in parse\n    raise ValueError(\"\\n\" + ParseException.explain(err, 0)) from None\nValueError: \n\\u23ce\n^\nParseFatalException: Unknown symbol: \\u, found '\\'  (at char 0), (line:1, col:1)\n```\n\n### Expected outcome\n\nThe unicode character and no exception.\n\n### Additional information\n\n\u003cdetails\u003e\u003csummary\u003ercParams\u003c/summary\u003e\n\n```python\nRcParams({'_internal.classic_mode': False,\n          'agg.path.chunksize': 0,\n          'animation.bitrate': -1,\n          'animation.codec': 'h264',\n          'animation.convert_args': ['-layers', 'OptimizePlus'],\n          'animation.convert_path': 'convert',\n          'animation.embed_limit': 20.0,\n          'animation.ffmpeg_args': [],\n          'animation.ffmpeg_path': 'ffmpeg',\n          'animation.frame_format': 'png',\n          'animation.html': 'none',\n          'animation.writer': 'ffmpeg',\n          'axes.autolimit_mode': 'data',\n          'axes.axisbelow': 'line',\n          'axes.edgecolor': 'black',\n          'axes.facecolor': 'white',\n          'axes.formatter.limits': [-5, 6],\n          'axes.formatter.min_exponent': 0,\n          'axes.formatter.offset_threshold': 4,\n          'axes.formatter.use_locale': False,\n          'axes.formatter.use_mathtext': False,\n          'axes.formatter.useoffset': True,\n          'axes.grid': False,\n          'axes.grid.axis': 'both',\n          'axes.grid.which': 'major',\n          'axes.labelcolor': 'black',\n          'axes.labelpad': 4.0,\n          'axes.labelsize': 'medium',\n          'axes.labelweight': 'normal',\n          'axes.linewidth': 0.8,\n          'axes.prop_cycle': cycler('color', ['#1f77b4', '#ff7f0e', '#2ca02c', '#d62728', '#9467bd', '#8c564b', '#e377c2', '#7f7f7f', '#bcbd22', '#17becf']),\n          'axes.spines.bottom': True,\n          'axes.spines.left': True,\n          'axes.spines.right': True,\n          'axes.spines.top': True,\n          'axes.titlecolor': 'auto',\n          'axes.titlelocation': 'center',\n          'axes.titlepad': 6.0,\n          'axes.titlesize': 'large',\n          'axes.titleweight': 'normal',\n          'axes.titley': None,\n          'axes.unicode_minus': True,\n          'axes.xmargin': 0.05,\n          'axes.ymargin': 0.05,\n          'axes.zmargin': 0.05,\n          'axes3d.automargin': False,\n          'axes3d.grid': True,\n          'axes3d.mouserotationstyle': 'arcball',\n          'axes3d.trackballborder': 0.2,\n          'axes3d.trackballsize': 0.667,\n          'axes3d.xaxis.panecolor': (0.95, 0.95, 0.95, 0.5),\n          'axes3d.yaxis.panecolor': (0.9, 0.9, 0.9, 0.5),\n          'axes3d.zaxis.panecolor': (0.925, 0.925, 0.925, 0.5),\n          'backend': 'qtagg',\n          'backend_fallback': True,\n          'boxplot.bootstrap': None,\n          'boxplot.boxprops.color': 'black',\n          'boxplot.boxprops.linestyle': '-',\n          'boxplot.boxprops.linewidth': 1.0,\n          'boxplot.capprops.color': 'black',\n          'boxplot.capprops.linestyle': '-',\n          'boxplot.capprops.linewidth': 1.0,\n          'boxplot.flierprops.color': 'black',\n          'boxplot.flierprops.linestyle': 'none',\n          'boxplot.flierprops.linewidth': 1.0,\n          'boxplot.flierprops.marker': 'o',\n          'boxplot.flierprops.markeredgecolor': 'black',\n          'boxplot.flierprops.markeredgewidth': 1.0,\n          'boxplot.flierprops.markerfacecolor': 'none',\n          'boxplot.flierprops.markersize': 6.0,\n          'boxplot.meanline': False,\n          'boxplot.meanprops.color': 'C2',\n          'boxplot.meanprops.linestyle': '--',\n          'boxplot.meanprops.linewidth': 1.0,\n          'boxplot.meanprops.marker': '^',\n          'boxplot.meanprops.markeredgecolor': 'C2',\n          'boxplot.meanprops.markerfacecolor': 'C2',\n          'boxplot.meanprops.markersize': 6.0,\n          'boxplot.medianprops.color': 'C1',\n          'boxplot.medianprops.linestyle': '-',\n          'boxplot.medianprops.linewidth': 1.0,\n          'boxplot.notch': False,\n          'boxplot.patchartist': False,\n          'boxplot.showbox': True,\n          'boxplot.showcaps': True,\n          'boxplot.showfliers': True,\n          'boxplot.showmeans': False,\n          'boxplot.vertical': True,\n          'boxplot.whiskerprops.color': 'black',\n          'boxplot.whiskerprops.linestyle': '-',\n          'boxplot.whiskerprops.linewidth': 1.0,\n          'boxplot.whiskers': 1.5,\n          'contour.algorithm': 'mpl2014',\n          'contour.corner_mask': True,\n          'contour.linewidth': None,\n          'contour.negative_linestyle': 'dashed',\n          'date.autoformatter.day': '%Y-%m-%d',\n          'date.autoformatter.hour': '%m-%d %H',\n          'date.autoformatter.microsecond': '%M:%S.%f',\n          'date.autoformatter.minute': '%d %H:%M',\n          'date.autoformatter.month': '%Y-%m',\n          'date.autoformatter.second': '%H:%M:%S',\n          'date.autoformatter.year': '%Y',\n          'date.converter': 'auto',\n          'date.epoch': '1970-01-01T00:00:00',\n          'date.interval_multiples': True,\n          'docstring.hardcopy': False,\n          'errorbar.capsize': 0.0,\n          'figure.autolayout': False,\n          'figure.constrained_layout.h_pad': 0.04167,\n          'figure.constrained_layout.hspace': 0.02,\n          'figure.constrained_layout.use': False,\n          'figure.constrained_layout.w_pad': 0.04167,\n          'figure.constrained_layout.wspace': 0.02,\n          'figure.dpi': 100.0,\n          'figure.edgecolor': 'white',\n          'figure.facecolor': 'white',\n          'figure.figsize': [6.4, 4.8],\n          'figure.frameon': True,\n          'figure.hooks': [],\n          'figure.labelsize': 'large',\n          'figure.labelweight': 'normal',\n          'figure.max_open_warning': 20,\n          'figure.raise_window': True,\n          'figure.subplot.bottom': 0.11,\n          'figure.subplot.hspace': 0.2,\n          'figure.subplot.left': 0.125,\n          'figure.subplot.right': 0.9,\n          'figure.subplot.top': 0.88,\n          'figure.subplot.wspace': 0.2,\n          'figure.titlesize': 'large',\n          'figure.titleweight': 'normal',\n          'font.cursive': ['Apple Chancery',\n                           'Textile',\n                           'Zapf Chancery',\n                           'Sand',\n                           'Script MT',\n                           'Felipa',\n                           'Comic Neue',\n                           'Comic Sans MS',\n                           'cursive'],\n          'font.family': ['sans-serif'],\n          'font.fantasy': ['Chicago',\n                           'Charcoal',\n                           'Impact',\n                           'Western',\n                           'xkcd script',\n                           'fantasy'],\n          'font.monospace': ['DejaVu Sans Mono',\n                             'Bitstream Vera Sans Mono',\n                             'Computer Modern Typewriter',\n                             'Andale Mono',\n                             'Nimbus Mono L',\n                             'Courier New',\n                             'Courier',\n                             'Fixed',\n                             'Terminal',\n                             'monospace'],\n          'font.sans-serif': ['DejaVu Sans',\n                              'Bitstream Vera Sans',\n                              'Computer Modern Sans Serif',\n                              'Lucida Grande',\n                              'Verdana',\n                              'Geneva',\n                              'Lucid',\n                              'Arial',\n                              'Helvetica',\n                              'Avant Garde',\n                              'sans-serif'],\n          'font.serif': ['DejaVu Serif',\n                         'Bitstream Vera Serif',\n                         'Computer Modern Roman',\n                         'New Century Schoolbook',\n                         'Century Schoolbook L',\n                         'Utopia',\n                         'ITC Bookman',\n                         'Bookman',\n                         'Nimbus Roman No9 L',\n                         'Times New Roman',\n                         'Times',\n                         'Palatino',\n                         'Charter',\n                         'serif'],\n          'font.size': 10.0,\n          'font.stretch': 'normal',\n          'font.style': 'normal',\n          'font.variant': 'normal',\n          'font.weight': 'normal',\n          'grid.alpha': 1.0,\n          'grid.color': '#b0b0b0',\n          'grid.linestyle': '-',\n          'grid.linewidth': 0.8,\n          'hatch.color': 'black',\n          'hatch.linewidth': 1.0,\n          'hist.bins': 10,\n          'image.aspect': 'equal',\n          'image.cmap': 'viridis',\n          'image.composite_image': True,\n          'image.interpolation': 'auto',\n          'image.interpolation_stage': 'auto',\n          'image.lut': 256,\n          'image.origin': 'upper',\n          'image.resample': True,\n          'interactive': False,\n          'keymap.back': ['left', 'c', 'backspace', 'MouseButton.BACK'],\n          'keymap.copy': ['ctrl+c', 'cmd+c'],\n          'keymap.forward': ['right', 'v', 'MouseButton.FORWARD'],\n          'keymap.fullscreen': ['f', 'ctrl+f'],\n          'keymap.grid': ['g'],\n          'keymap.grid_minor': ['G'],\n          'keymap.help': ['f1'],\n          'keymap.home': ['h', 'r', 'home'],\n          'keymap.pan': ['p'],\n          'keymap.quit': ['ctrl+w', 'cmd+w', 'q'],\n          'keymap.quit_all': [],\n          'keymap.save': ['s', 'ctrl+s'],\n          'keymap.xscale': ['k', 'L'],\n          'keymap.yscale': ['l'],\n          'keymap.zoom': ['o'],\n          'legend.borderaxespad': 0.5,\n          'legend.borderpad': 0.4,\n          'legend.columnspacing': 2.0,\n          'legend.edgecolor': '0.8',\n          'legend.facecolor': 'inherit',\n          'legend.fancybox': True,\n          'legend.fontsize': 'medium',\n          'legend.framealpha': 0.8,\n          'legend.frameon': True,\n          'legend.handleheight': 0.7,\n          'legend.handlelength': 2.0,\n          'legend.handletextpad': 0.8,\n          'legend.labelcolor': 'None',\n          'legend.labelspacing': 0.5,\n          'legend.loc': 'best',\n          'legend.markerscale': 1.0,\n          'legend.numpoints': 1,\n          'legend.scatterpoints': 1,\n          'legend.shadow': False,\n          'legend.title_fontsize': None,\n          'lines.antialiased': True,\n          'lines.color': 'C0',\n          'lines.dash_capstyle': \u003cCapStyle.butt: 'butt'\u003e,\n          'lines.dash_joinstyle': \u003cJoinStyle.round: 'round'\u003e,\n          'lines.dashdot_pattern': [6.4, 1.6, 1.0, 1.6],\n          'lines.dashed_pattern': [3.7, 1.6],\n          'lines.dotted_pattern': [1.0, 1.65],\n          'lines.linestyle': '-',\n          'lines.linewidth': 1.5,\n          'lines.marker': 'None',\n          'lines.markeredgecolor': 'auto',\n          'lines.markeredgewidth': 1.0,\n          'lines.markerfacecolor': 'auto',\n          'lines.markersize': 6.0,\n          'lines.scale_dashes': True,\n          'lines.solid_capstyle': \u003cCapStyle.projecting: 'projecting'\u003e,\n          'lines.solid_joinstyle': \u003cJoinStyle.round: 'round'\u003e,\n          'macosx.window_mode': 'system',\n          'markers.fillstyle': 'full',\n          'mathtext.bf': 'sans:bold',\n          'mathtext.bfit': 'sans:italic:bold',\n          'mathtext.cal': 'cursive',\n          'mathtext.default': 'it',\n          'mathtext.fallback': 'cm',\n          'mathtext.fontset': 'dejavusans',\n          'mathtext.it': 'sans:italic',\n          'mathtext.rm': 'sans',\n          'mathtext.sf': 'sans',\n          'mathtext.tt': 'monospace',\n          'patch.antialiased': True,\n          'patch.edgecolor': 'black',\n          'patch.facecolor': 'C0',\n          'patch.force_edgecolor': False,\n          'patch.linewidth': 1.0,\n          'path.effects': [],\n          'path.simplify': True,\n          'path.simplify_threshold': 0.111111111111,\n          'path.sketch': None,\n          'path.snap': True,\n          'pcolor.shading': 'auto',\n          'pcolormesh.snap': True,\n          'pdf.compression': 6,\n          'pdf.fonttype': 3,\n          'pdf.inheritcolor': False,\n          'pdf.use14corefonts': False,\n          'pgf.preamble': '',\n          'pgf.rcfonts': True,\n          'pgf.texsystem': 'xelatex',\n          'polaraxes.grid': True,\n          'ps.distiller.res': 6000,\n          'ps.fonttype': 3,\n          'ps.papersize': 'letter',\n          'ps.useafm': False,\n          'ps.usedistiller': None,\n          'savefig.bbox': None,\n          'savefig.directory': '~',\n          'savefig.dpi': 'figure',\n          'savefig.edgecolor': 'auto',\n          'savefig.facecolor': 'auto',\n          'savefig.format': 'png',\n          'savefig.orientation': 'portrait',\n          'savefig.pad_inches': 0.1,\n          'savefig.transparent': False,\n          'scatter.edgecolors': 'face',\n          'scatter.marker': 'o',\n          'svg.fonttype': 'path',\n          'svg.hashsalt': None,\n          'svg.id': None,\n          'svg.image_inline': True,\n          'text.antialiased': True,\n          'text.color': 'black',\n          'text.hinting': 'force_autohint',\n          'text.hinting_factor': 8,\n          'text.kerning_factor': 0,\n          'text.latex.preamble': '',\n          'text.parse_math': True,\n          'text.usetex': False,\n          'timezone': 'UTC',\n          'tk.window_focus': False,\n          'toolbar': 'toolbar2',\n          'webagg.address': '127.0.0.1',\n          'webagg.open_in_browser': True,\n          'webagg.port': 8988,\n          'webagg.port_retries': 50,\n          'xaxis.labellocation': 'center',\n          'xtick.alignment': 'center',\n          'xtick.bottom': True,\n          'xtick.color': 'black',\n          'xtick.direction': 'out',\n          'xtick.labelbottom': True,\n          'xtick.labelcolor': 'inherit',\n          'xtick.labelsize': 'medium',\n          'xtick.labeltop': False,\n          'xtick.major.bottom': True,\n          'xtick.major.pad': 3.5,\n          'xtick.major.size': 3.5,\n          'xtick.major.top': True,\n          'xtick.major.width': 0.8,\n          'xtick.minor.bottom': True,\n          'xtick.minor.ndivs': 'auto',\n          'xtick.minor.pad': 3.4,\n          'xtick.minor.size': 2.0,\n          'xtick.minor.top': True,\n          'xtick.minor.visible': False,\n          'xtick.minor.width': 0.6,\n          'xtick.top': False,\n          'yaxis.labellocation': 'center',\n          'ytick.alignment': 'center_baseline',\n          'ytick.color': 'black',\n          'ytick.direction': 'out',\n          'ytick.labelcolor': 'inherit',\n          'ytick.labelleft': True,\n          'ytick.labelright': False,\n          'ytick.labelsize': 'medium',\n          'ytick.left': True,\n          'ytick.major.left': True,\n          'ytick.major.pad': 3.5,\n          'ytick.major.right': True,\n          'ytick.major.size': 3.5,\n          'ytick.major.width': 0.8,\n          'ytick.minor.left': True,\n          'ytick.minor.ndivs': 'auto',\n          'ytick.minor.pad': 3.4,\n          'ytick.minor.right': True,\n          'ytick.minor.size': 2.0,\n          'ytick.minor.visible': False,\n          'ytick.minor.width': 0.6,\n          'ytick.right': False})\n```\n\u003c/details\u003e\n\n### Operating system\n\nManjaro\n\n### Matplotlib Version\n\n3.10.5, 3.10.1\n\n### Matplotlib Backend\n\nqtagg\n\n### Python version\n\n3.13.7\n\n### Jupyter version\n\nn/a\n\n### Installation\n\nLinux package manager, pip","author":{"url":"https://github.com/mahlzahn","@type":"Person","name":"mahlzahn"},"datePublished":"2025-09-17T11:51:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/30574/matplotlib/issues/30574"}