René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Crash when removing contour set after removing contour labels","articleBody":"### Bug summary\n\nCreate a contour plot `CS`, add contour labels based on `CS`, remove the contour labels, then remove `CS`. \n\n### Code for reproduction\n\n```Python\nimport matplotlib.pyplot as plt\nimport numpy as np\n\ndelta = 0.025\nx = np.arange(-3.0, 3.0, delta)\ny = np.arange(-2.0, 2.0, delta)\nX, Y = np.meshgrid(x, y)\nZ1 = np.exp(-X**2 - Y**2)\nZ2 = np.exp(-(X - 1)**2 - (Y - 1)**2)\nZ = (Z1 - Z2) * 2\n\nfig, ax = plt.subplots()\nax.contourf(X, Y, Z)\nCS = ax.contour(X, Y, Z, visible=False)\nlabels = ax.clabel(CS, colors='k')\nfor label in labels: label.remove()\nlabels = ax.clabel(CS, colors='r')\nCS.remove()\n```\n\n### Actual outcome\n\n---------------------------------------------------------------------------\nValueError                                Traceback (most recent call last)\nCell In[1], line 18\n     16 for label in labels: label.remove()\n     17 labels = ax.clabel(CS, colors='r')\n---\u003e 18 CS.remove()\n\nFile ~/dataviz-render-update-testing/matplotlib/lib/matplotlib/contour.py:518, in ContourLabeler.remove(self)\n    516 super().remove()\n    517 for text in self.labelTexts:\n--\u003e 518     text.remove()\n\nFile ~/dataviz-render-update-testing/matplotlib/lib/matplotlib/artist.py:254, in Artist.remove(self)\n    249 # There is no method to set the callback.  Instead, the parent should\n    250 # set the _remove_method attribute directly.  This would be a\n    251 # protected attribute if Python supported that sort of thing.  The\n    252 # callback has one parameter, which is the child to be removed.\n    253 if self._remove_method is not None:\n--\u003e 254     self._remove_method(self)\n    255     # clear stale callback\n    256     self.stale_callback = None\n\nValueError: list.remove(x): x not in list\n\n\n### Expected outcome\n\n\u003cimg width=\"559\" height=\"413\" alt=\"Image\" src=\"https://github.com/user-attachments/assets/9a2bcbca-2a0c-455a-884b-70cd562210d2\" /\u003e\n\n### Additional information\n\n_No response_\n\n### Operating system\n\n_No response_\n\n### Matplotlib Version\n\n0.2.0.dev53961+unknown.g607d2c380.g9e38f5437\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n_No response_\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\nNone","author":{"url":"https://github.com/williamlus","@type":"Person","name":"williamlus"},"datePublished":"2026-03-27T05:27:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":19},"url":"https://github.com/31404/matplotlib/issues/31404"}