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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Removing axes created by twiny() leads to an error","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nRemoving axes created with twiny() leads to an error. I have found a very similar bug to my issue here: #14911. Interestingly enough this works with twinx(). The code in the original bug report also works in my installation.\r\n\r\n**Code for reproduction**\r\n\r\n\u003c!--A minimum code snippet required to reproduce the bug.\r\nPlease make sure to minimize the number of dependencies required, and provide\r\nany necessary plotted data.\r\nAvoid using threads, as Matplotlib is (explicitly) not thread-safe.--\u003e\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\n\r\nfig, ax = plt.subplots()\r\nax_twin = ax.twiny()\r\nax_twin.remove()\r\nplt.show()\r\n```\r\n\r\n**Actual outcome**\r\n\r\n\u003c!--The output produced by the above code, which may be a screenshot, console output, etc.--\u003e\r\n\r\n```\r\nException in Tkinter callback\r\nTraceback (most recent call last):\r\n  File \"c:\\programdata\\miniconda3\\lib\\tkinter\\__init__.py\", line 1883, in __call__\r\n    return self.func(*args)\r\n  File \"c:\\programdata\\miniconda3\\lib\\tkinter\\__init__.py\", line 804, in callit\r\n    func(*args)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\backends\\_backend_tk.py\", line 253, in idle_draw\r\n    self.draw()\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\backends\\backend_tkagg.py\", line 9, in draw\r\n    super(FigureCanvasTkAgg, self).draw()\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\backends\\backend_agg.py\", line 407, in draw\r\n    self.figure.draw(self.renderer)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\artist.py\", line 41, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\figure.py\", line 1863, in draw\r\n    mimage._draw_list_compositing_images(\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\image.py\", line 131, in _draw_list_compositing_images\r\n    a.draw(renderer)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\artist.py\", line 41, in draw_wrapper\r\n    return draw(artist, renderer, *args, **kwargs)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\cbook\\deprecation.py\", line 411, in wrapper\r\n    return func(*inner_args, **inner_kwargs)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 2707, in draw\r\n    self._update_title_position(renderer)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axes\\_base.py\", line 2638, in _update_title_position\r\n    bb = ax.xaxis.get_tightbbox(renderer)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axis.py\", line 1109, in get_tightbbox\r\n    ticks_to_draw = self._update_ticks()\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axis.py\", line 1021, in _update_ticks\r\n    major_locs = self.get_majorticklocs()\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axis.py\", line 1283, in get_majorticklocs\r\n    return self.major.locator()\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\ticker.py\", line 2276, in __call__\r\n    return self.tick_values(vmin, vmax)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\ticker.py\", line 2284, in tick_values\r\n    locs = self._raw_ticks(vmin, vmax)\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\ticker.py\", line 2223, in _raw_ticks\r\n    nbins = np.clip(self.axis.get_tick_space(),\r\n  File \"c:\\programdata\\miniconda3\\lib\\site-packages\\matplotlib\\axis.py\", line 2243, in get_tick_space\r\n    length = ((ends[1][0] - ends[0][0]) / self.axes.figure.dpi) * 72\r\nAttributeError: 'NoneType' object has no attribute 'dpi'\r\n\r\n```\r\n\r\n**Expected outcome**\r\n\r\nA plot with the twiny axes removed\r\n\r\n\u003c!--A description of the expected outcome from the code snippet--\u003e\r\n\u003c!--If this used to work in an earlier version of Matplotlib, please note the version it used to work on--\u003e\r\n\r\n**Matplotlib version**\r\n\u003c!--Please specify your platform and versions of the relevant libraries you are using:--\u003e\r\n  * Operating system: Windows 10\r\n  * Matplotlib version: 3.3.2\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`): TkAgg\r\n  * Python version: 3.8.3\r\n\r\n\u003c!--Please tell us how you installed matplotlib and python e.g., from source, pip, conda--\u003e\r\n\u003c!--If you installed from conda, please specify which channel you used if not the default--\u003e\r\nPython is from miniconda, all packages installed via pip.\r\n\r\n","author":{"url":"https://github.com/lars-sowa-snkeos","@type":"Person","name":"lars-sowa-snkeos"},"datePublished":"2020-11-10T14:34:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/18925/matplotlib/issues/18925"}