René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: `ValueError` upon deepcopy of a `Figure` object","articleBody":"### Bug summary\r\n\r\nA deepcopy of a `Figure` object results in `ValueError: 'Spines' object does not contain a '__deepcopy__' spine`.\r\n\r\nThis issue surfaced in a bug report of `schemdraw`: https://bitbucket.org/cdelker/schemdraw/issues/56/copydeepcopy-drawing-fails Nevertheless, the current issue is unrelated to `schemdraw`. I'm just mentioning this to illustrate a relevant use case leading to this problem.\r\n\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport matplotlib.pyplot as plt\r\nimport copy\r\nfig, ax = plt.subplots()\r\ncopy.deepcopy(fig)\r\n```\r\n\r\nDisclaimer: this is taken from a message of `cdelker` on https://bitbucket.org/cdelker/schemdraw/issues/56/copydeepcopy-drawing-fails\r\n\r\n\r\n### Actual outcome\r\n\r\n```\r\nTraceback (most recent call last):\r\n  File \"/usr/lib64/python3.9/site-packages/matplotlib/spines.py\", line 551, in __getattr__\r\n    return self._dict[name]\r\nKeyError: '__deepcopy__'\r\n\r\nDuring handling of the above exception, another exception occurred:\r\n\r\nTraceback (most recent call last):\r\n  File \"\u003cstdin\u003e\", line 1, in \u003cmodule\u003e\r\n  File \"/usr/lib64/python3.9/copy.py\", line 172, in deepcopy\r\n    y = _reconstruct(x, memo, *rv)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 270, in _reconstruct\r\n    state = deepcopy(state, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 146, in deepcopy\r\n    y = copier(x, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 230, in _deepcopy_dict\r\n    y[deepcopy(key, memo)] = deepcopy(value, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 172, in deepcopy\r\n    y = _reconstruct(x, memo, *rv)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 270, in _reconstruct\r\n    state = deepcopy(state, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 146, in deepcopy\r\n    y = copier(x, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 230, in _deepcopy_dict\r\n    y[deepcopy(key, memo)] = deepcopy(value, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 146, in deepcopy\r\n    y = copier(x, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 205, in _deepcopy_list\r\n    append(deepcopy(a, memo))\r\n  File \"/usr/lib64/python3.9/copy.py\", line 146, in deepcopy\r\n    y = copier(x, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 210, in _deepcopy_tuple\r\n    y = [deepcopy(a, memo) for a in x]\r\n  File \"/usr/lib64/python3.9/copy.py\", line 210, in \u003clistcomp\u003e\r\n    y = [deepcopy(a, memo) for a in x]\r\n  File \"/usr/lib64/python3.9/copy.py\", line 172, in deepcopy\r\n    y = _reconstruct(x, memo, *rv)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 270, in _reconstruct\r\n    state = deepcopy(state, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 146, in deepcopy\r\n    y = copier(x, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 230, in _deepcopy_dict\r\n    y[deepcopy(key, memo)] = deepcopy(value, memo)\r\n  File \"/usr/lib64/python3.9/copy.py\", line 151, in deepcopy\r\n    copier = getattr(x, \"__deepcopy__\", None)\r\n  File \"/usr/lib64/python3.9/site-packages/matplotlib/spines.py\", line 553, in __getattr__\r\n    raise ValueError(\r\nValueError: 'Spines' object does not contain a '__deepcopy__' spine\r\n```\r\n\r\n### Expected outcome\r\n\r\nEither a deepcopy of the figure or a meaningful error message explaining that this operation is not supported.\r\n\r\n### Operating system\r\n\r\nFedora Linux\r\n\r\n### Matplotlib Version\r\n\r\n3.4.3\r\n\r\n### Matplotlib Backend\r\n\r\nQt5Agg\r\n\r\n### Python version\r\n\r\n3.9.7\r\n\r\n### Jupyter version\r\n\r\n6.1.6, (not installed)\r\n\r\n### Other libraries\r\n\r\nNone\r\n\r\n### Installation\r\n\r\nLinux package manager (Debian/Fedora/etc.)\r\n\r\n### Conda channel\r\n\r\n_No response_","author":{"url":"https://github.com/tovrstra","@type":"Person","name":"tovrstra"},"datePublished":"2021-11-06T17:57:08.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/21554/matplotlib/issues/21554"}