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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Setting exactly 2 colors with tuple in `plot` method gives confusing error","articleBody":"### Bug summary\n\nIf one attempts to set the `color` parameter to a tuple of length 2, a nonsense error message is returned.\n\n### Code for reproduction\n\n```Python\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\nx = np.linspace(0, 10, 100)\r\ny = np.array([np.sin(x), np.cos(x)]).T\r\n\r\nplt.plot(x, y, label=(\"sin(x)\", \"cos(x)\")) # works\r\nplt.plot(x, y, label=(\"sin(x)\", \"cos(x)\"), color=(\"red\", \"blue\")) # causes strange error\r\nplt.legend()\r\nplt.show()\n```\n\n\n### Actual outcome\n\nTraceback (most recent call last):\r\n  File \"/Users/miles/Desktop/thing.py\", line 8, in \u003cmodule\u003e\r\n    plt.plot(x, y, label=(\"sin(x)\", \"cos(x)\"), color=(\"red\", \"blue\")) # causes error\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/pyplot.py\", line 3708, in plot\r\n    return gca().plot(\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_axes.py\", line 1779, in plot\r\n    lines = [*self._get_lines(self, *args, data=data, **kwargs)]\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_base.py\", line 296, in __call__\r\n    yield from self._plot_args(\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_base.py\", line 534, in _plot_args\r\n    return [l[0] for l in result]\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_base.py\", line 534, in \u003clistcomp\u003e\r\n    return [l[0] for l in result]\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_base.py\", line 527, in \u003cgenexpr\u003e\r\n    result = (make_artist(axes, x[:, j % ncx], y[:, j % ncy], kw,\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/axes/_base.py\", line 335, in _makeline\r\n    seg = mlines.Line2D(x, y, **kw)\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/lines.py\", line 376, in __init__\r\n    self.set_color(color)\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/lines.py\", line 1066, in set_color\r\n    mcolors._check_color_like(color=color)\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/colors.py\", line 245, in _check_color_like\r\n    if not is_color_like(v):\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/colors.py\", line 227, in is_color_like\r\n    to_rgba(c)\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/colors.py\", line 309, in to_rgba\r\n    rgba = _to_rgba_no_colorcycle(c, alpha)\r\n  File \"/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/matplotlib/colors.py\", line 334, in _to_rgba_no_colorcycle\r\n    if alpha is not None and not 0 \u003c= alpha \u003c= 1:\r\nTypeError: '\u003c=' not supported between instances of 'int' and 'str'\n\n### Expected outcome\n\nEither: (1) works as expected as passing a tuple to `label` does, or, if this won't be supported, (2) a more sensical error message is returned, like if `[\"red\", \"blue\"]` were passed.\n\n### Additional information\n\nThis difficult-to-interpret error seems to be caused by the `if` statement of line 328 in `_to_rgba_no_colorcycle` in `colors.py`, which says `if isinstance(c, tuple) and len(c) == 2`. If I comment out this `if` statement, then the error message gives the normal `ValueError: ('red', 'blue') is not a valid value for color...` message. Of course, it would be great if multiple colors were supported here, but I understand if there is a bigger reason why it is not supported.\n\n### Operating system\n\nmacOS 14.4.1\n\n### Matplotlib Version\n\n3.9.0\n\n### Matplotlib Backend\n\nmacosx\n\n### Python version\n\n3.9.6\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\npip","author":{"url":"https://github.com/miles-1","@type":"Person","name":"miles-1"},"datePublished":"2024-06-21T18:43:44.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/28434/matplotlib/issues/28434"}