René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Markers with string-type integer values are converted to integers in cycler and matplotlibrc","articleBody":"### Bug summary\n\nWhen creating a cycler with a `\"marker\"` property value contains strings that _could_ be converted to integers, they are always converted to integers, even if the string value is valid and the intended value. This is most obvious with the list `[\"1\", \"2\"]`; which is distinctly different from `[1, 2]`. However, the latter is always used. **Edit (20.02.2025):** This is also the case for `\"lines.markers\"`, `\"boxplot.flierprops.marker\"`, `\"boxplot.meanprops.marker\"`, and `\"scatter.marker\"`.\n\nRelevant functions are `_validate_markers` ([here](https://github.com/matplotlib/matplotlib/blob/7ede0929dc39858a2801f8b6b2711db0d4fa5bfe/lib/matplotlib/rcsetup.py#L231)) and `_listify_validator` ([here](https://github.com/matplotlib/matplotlib/blob/7ede0929dc39858a2801f8b6b2711db0d4fa5bfe/lib/matplotlib/rcsetup.py#L97)). It seems like this issue was introduced by #27613, which solved a similar issue reported in #27596.\n\n### Code for reproduction\n**Edited 20.02.2025**\n```Python\nfrom matplotlib import cycler\nimport matplotlib.pyplot as plt\n\nmarkers = [\"1\", \"2\", \"o\", 4]\nprint(\"Cycler\")\ntest_cycler = cycler(\"marker\", markers)\nfor prop_dict in test_cycler:\n    print(\n        \"Marker {} with type {}.\".format(prop_dict[\"marker\"], type(prop_dict[\"marker\"]))\n    )\nprint(\"lines.marker\")\nfor marker in markers:\n    plt.rcParams[\"lines.marker\"] = marker\n    print(\n        \"Marker {} with type {}.\".format(\n            plt.rcParams[\"lines.marker\"], type(plt.rcParams[\"lines.marker\"])\n        )\n    )\n```\n\n### Actual outcome\n\n```bash\n$ python main.py\nCycler\nMarker 1 with type \u003cclass 'int'\u003e.\nMarker 2 with type \u003cclass 'int'\u003e.\nMarker o with type \u003cclass 'str'\u003e.\nMarker 4 with type \u003cclass 'int'\u003e.\nlines.marker\nMarker 1 with type \u003cclass 'int'\u003e.\nMarker 2 with type \u003cclass 'int'\u003e.\nMarker o with type \u003cclass 'str'\u003e.\nMarker 4 with type \u003cclass 'int'\u003e.\n```\nwhich indicates that the string entries `\"1\"` and `\"2\"` are converted into integers. As the string `\"o\"` cannot be converted into an integer with `int(\"o\")`, it is used explicitly.\n\n### Expected outcome\n\n```bash\n$ python main.py\nCycler\nMarker 1 with type \u003cclass 'str'\u003e.\nMarker 2 with type \u003cclass 'str'\u003e.\nMarker o with type \u003cclass 'str'\u003e.\nMarker 4 with type \u003cclass 'int'\u003e.\nlines.marker\nMarker 1 with type \u003cclass 'str'\u003e.\nMarker 2 with type \u003cclass 'str'\u003e.\nMarker o with type \u003cclass 'str'\u003e.\nMarker 4 with type \u003cclass 'int'\u003e.\n```\nThis output would indicate that strings containing integers are parsed correctly.\n\n### Additional information\n\nThis bug was not present prior to #27613, but it did solve a similar bug.\n\nLooking at the code which causes this bug, `_validate_markers` ([here](https://github.com/matplotlib/matplotlib/blob/7ede0929dc39858a2801f8b6b2711db0d4fa5bfe/lib/matplotlib/rcsetup.py#L231)) and `_listify_validator` ([here](https://github.com/matplotlib/matplotlib/blob/7ede0929dc39858a2801f8b6b2711db0d4fa5bfe/lib/matplotlib/rcsetup.py#L97)), it's not clear to me why the validation is done this way. I.e., to validate types, values are explicitly converted to see if a `ValueError` is raised, instead of testing the type explicitly. Is this the intended method for validation?\n\n~~I have a draft solution, but I would like clarification on the intended validation mechanisms before I submit the code for review.~~ **Edit (20.02.2025):** Since finding that other RcParams entries are affected by this bug, my solution is no longer applicable.\n\n### Operating system\n\nFedora 41\n\n### Matplotlib Version\n\n3.10.0\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\nPython 3.12.9\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\npip","author":{"url":"https://github.com/conradhaupt","@type":"Person","name":"conradhaupt"},"datePublished":"2025-02-19T12:48:32.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/29646/matplotlib/issues/29646"}