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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: plt.savefig leaks the stack","articleBody":"### Bug summary\r\n\r\nCalling `plt.savefig` leaks local variables from parent calling functions. These can be found in `gc.get_objects()` and are cleared by `gc.collect()`\r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport gc\r\nimport matplotlib.pyplot as plt\r\n\r\n\r\nclass SomeObject:\r\n    pass\r\n\r\ndef save_plots():\r\n    plt.plot([1, 2, 3])\r\n    plt.savefig(\"test.png\")\r\n\r\ndef leaky():\r\n    some_object = SomeObject()\r\n    save_plots()\r\n\r\nleaky()\r\n\r\nfor obj in gc.get_objects():\r\n    try:\r\n        if isinstance(obj, SomeObject):\r\n            print(\"Object is leaking\")\r\n    except:\r\n        pass\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\n`Object is leaking`\r\n\r\n### Expected outcome\r\n\r\nNothing should be printed.\r\n\r\n### Additional information\r\n\r\n- I initially found this bug because I realized my deep learning training loop was leaking VRAM. Torch tensors were being kept in memory when `Figure.savefig` was called\r\n- I am under the impression that `ExitStack` within `savefig` is meant to hack around this issue but is somehow not working in my case?\r\n- I have been through issue #23701, but here I am able to provide a short and reproducible example\r\n- I have been through #20490 as well, but the issue persists with the `agg` backend\r\n- It is not acceptable to have to call `gc.collect()`. Most users won't be aware of the issue. Given the prevalence of deep learning these days, it's likely objects leaking into GPU memory will be a common problem due to this bug.\r\n\r\n### Operating system\r\n\r\nWin10 x64\r\n\r\n### Matplotlib Version\r\n\r\n3.7.1\r\n\r\n### Matplotlib Backend\r\n\r\nTkAgg\r\n\r\n### Python version\r\n\r\n3.10.0\r\n\r\n### Jupyter version\r\n\r\n_No response_\r\n\r\n### Installation\r\n\r\npip","author":{"url":"https://github.com/CorentinJ","@type":"Person","name":"CorentinJ"},"datePublished":"2023-03-07T13:11:25.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":24},"url":"https://github.com/25406/matplotlib/issues/25406"}