René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Figure cannot be closed if it has associated Agg canvas","articleBody":"### Bug report\r\n\r\n** plt.fignum_exists() returns True after figure is closed**\r\n\r\nCode snippet below closes figure after creating `FigureCanvasAgg`, and it works with matplotlib-3.2.1 but fails with matplotlib-3.3.0\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nimport matplotlib\r\nmatplotlib.use('Agg')\r\nimport matplotlib.pyplot as plt\r\n\r\nfigure = plt.figure()\r\nplt.axis('scaled')\r\nplt.tight_layout()\r\nmatplotlib.backends.backend_agg.FigureCanvasAgg(figure)\r\nplt.close(figure)\r\nprint(\"Matplotlib version:\", matplotlib.__version__)\r\nassert plt.fignum_exists(figure.number) == False\r\n```\r\n\r\n**Actual outcome**\r\n\r\n```\r\nMatplotlib version: 3.3.0\r\nTraceback (most recent call last):\r\n  File \"figure_exists.py\", line 11, in \u003cmodule\u003e\r\n    assert plt.fignum_exists(figure.number) == False\r\nAssertionError\r\n\r\n```\r\n\r\n**Expected outcome**\r\nNo assertion, which is easy to reproduce if one to downgrade to matplotlib-3.2.1:\r\n```\r\n pip3 install matplotlib==3.2.1 --user; python figure_exists.py \r\nCollecting matplotlib==3.2.1\r\n  Using cached https://files.pythonhosted.org/packages/b2/c2/71fcf957710f3ba1f09088b35776a799ba7dd95f7c2b195ec800933b276b/matplotlib-3.2.1-cp37-cp37m-manylinux1_x86_64.whl\r\nRequirement already satisfied: pyparsing!=2.0.4,!=2.1.2,!=2.1.6,\u003e=2.0.1 in /usr/lib/python3.7/site-packages (from matplotlib==3.2.1) (2.4.0)\r\nRequirement already satisfied: numpy\u003e=1.11 in /usr/local/lib64/python3.7/site-packages (from matplotlib==3.2.1) (1.18.4)\r\nRequirement already satisfied: python-dateutil\u003e=2.1 in /usr/lib/python3.7/site-packages (from matplotlib==3.2.1) (2.8.0)\r\nRequirement already satisfied: cycler\u003e=0.10 in /usr/lib/python3.7/site-packages (from matplotlib==3.2.1) (0.10.0)\r\nRequirement already satisfied: kiwisolver\u003e=1.0.1 in /usr/lib64/python3.7/site-packages (from matplotlib==3.2.1) (1.1.0)\r\nRequirement already satisfied: six\u003e=1.5 in /usr/lib/python3.7/site-packages (from python-dateutil\u003e=2.1-\u003ematplotlib==3.2.1) (1.12.0)\r\nRequirement already satisfied: setuptools in /usr/lib/python3.7/site-packages (from kiwisolver\u003e=1.0.1-\u003ematplotlib==3.2.1) (40.8.0)\r\nInstalling collected packages: matplotlib\r\n  Found existing installation: matplotlib 3.3.0\r\n    Uninstalling matplotlib-3.3.0:\r\n      Successfully uninstalled matplotlib-3.3.0\r\nSuccessfully installed matplotlib-3.2.1\r\nMatplotlib version: 3.2.1\r\n```\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: Fedora Core 30\r\n  * Matplotlib version: 3.3.0 (installed via pip as `pip3 install matplotlib==3.3.0 --user` )\r\n  * Matplotlib backend (`print(matplotlib.get_backend())`):\r\n  * Python version: 3.7.0\r\n  * Jupyter version (if applicable):\r\n  * Other libraries: \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\n\r\n","author":{"url":"https://github.com/malfet","@type":"Person","name":"malfet"},"datePublished":"2020-08-04T01:38:09.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/18163/matplotlib/issues/18163"}