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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"UserWarning: \"Trying to register the cmap '...' which already exists\" is not very helpful.","articleBody":"### Describe the issue\r\n\r\nMatplotlib 3.4 introduces a UserWarning with 1a9dacff1cb when attempting to register a color map by the same name twice.  So for a lame luser like myself, how am I to know if my colormap name has already been registered?  Is there public API to check if a given cmap name exists? \r\n\r\n### Proposed fix\r\n\r\nPresently, I only see this option via \"private\" API to check this situation\r\n\r\n```python\r\nfrom matplotlib import cm\r\n\r\ndef cmap_exists(name):\r\n     return name in cm.__builtin_cmaps\r\n```\r\n\r\nOtherwise, there would be this lame workaround\r\n\r\n```python\r\nfrom matplotlib import cm\r\n\r\ndef cmap_exists(name):\r\n    try:\r\n         cm.get_cmap(name)\r\n         return True\r\n    except ValueError:\r\n         pass\r\n    return False\r\n```\r\n\r\nHopefully I am not missing something obvious.  If something exists, it would be nice to enhance the UserWarning by saying \"Trying to register the cmap {name!r} which already exists. Please first check presence of cmap by calling `cm.cmap_exists(name)`\"\r\n\r\nThank you!","author":{"url":"https://github.com/akrherz","@type":"Person","name":"akrherz"},"datePublished":"2021-04-01T18:05:28.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/19842/matplotlib/issues/19842"}