René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Scatter plot with non-sequence ´c´ color should give a better Error message.","articleBody":"### Bug report\r\n\r\n**Bug summary**\r\n\r\nUsing a scatter plot with a single point at. But using a single number for the \"c\" keyword gave an slightly unhelpful error about a `TypeError` from `mcolors.to_rgba_array`. A `cmap` is used to map the number given but this is omitted here as the Error is still reproduced.\r\n\r\n\r\n**Code for reproduction**\r\n\r\n```python\r\nimport maptlotlib.pyplot as plt\r\nplt.scatter([0], [1], c=0.5)\r\n\r\n```\r\n\r\n**Actual outcome**\r\n\r\n```\r\n---------------------------------------------------------------------------\r\nTypeError                                 Traceback (most recent call last)\r\n\u003cipython-input-16-a8c544fd7de9\u003e in \u003cmodule\u003e()\r\n----\u003e 1 plt.scatter([0], [1], c=0.5)\r\n\r\n~/anaconda3/lib/python3.6/site-packages/matplotlib/pyplot.py in scatter(x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, hold, data, **kwargs)\r\n   3376                          vmin=vmin, vmax=vmax, alpha=alpha,\r\n   3377                          linewidths=linewidths, verts=verts,\r\n-\u003e 3378                          edgecolors=edgecolors, data=data, **kwargs)\r\n   3379     finally:\r\n   3380         ax._hold = washold\r\n\r\n~/anaconda3/lib/python3.6/site-packages/matplotlib/__init__.py in inner(ax, *args, **kwargs)\r\n   1715                     warnings.warn(msg % (label_namer, func.__name__),\r\n   1716                                   RuntimeWarning, stacklevel=2)\r\n-\u003e 1717             return func(ax, *args, **kwargs)\r\n   1718         pre_doc = inner.__doc__\r\n   1719         if pre_doc is None:\r\n\r\n~/anaconda3/lib/python3.6/site-packages/matplotlib/axes/_axes.py in scatter(self, x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, **kwargs)\r\n   3981             try:\r\n   3982                 # must be acceptable as PathCollection facecolors\r\n-\u003e 3983                 colors = mcolors.to_rgba_array(c)\r\n   3984             except ValueError:\r\n   3985                 # c not acceptable as PathCollection facecolor\r\n\r\n~/anaconda3/lib/python3.6/site-packages/matplotlib/colors.py in to_rgba_array(c, alpha)\r\n    229         pass\r\n    230     # Convert one at a time.\r\n--\u003e 231     result = np.empty((len(c), 4), float)\r\n    232     for i, cc in enumerate(c):\r\n    233         result[i] = to_rgba(cc, alpha)\r\n\r\nTypeError: object of type 'int' has no len()\r\n\r\n```\r\n\r\n**Expected outcome**\r\n\r\nHave a useful message from an `except TypeError:` from the failing `colors = mcolors.to_rgba_array(c)` call in line 3983 much like the `ValueError` except, would probably do it.\r\n\r\nHelpfully indicating that `c` must be the correct type (color, sequence, or sequence of color).\r\n\r\n_Note:_\r\nWith x, y, and c all as single numbers the scatter plot call runs without any errors raised, \r\ne.g. `plt.scatter(0, 1, c=0.5)`\r\n","author":{"url":"https://github.com/jason-neal","@type":"Person","name":"jason-neal"},"datePublished":"2018-02-01T23:51:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/10365/matplotlib/issues/10365"}