Improve error when passing 0d array to scatter().

anntzer · anntzer · commit eb38d25cce40 · 2019-12-09T01:12:12.000+01:00
With `scatter([1, 2], [3, 4], c=np.array(.5))`...

previously:

    &lt;elided&gt;
      File ".../matplotlib/colors.py", line 338, in to_rgba_array
        if len(c) == 0:
    TypeError: len() of unsized object

now

    &lt;elided&gt;
      File ".../matplotlib/axes/_axes.py", line 4249, in _parse_scatter_color_args
        raise invalid_shape_exception(c.size, xsize)
    ValueError: 'c' argument has 1 elements, which is inconsistent with 'x' and 'y' with size 2.

Essentially the problem is that np.array(.5) passes an
`isinstance(..., Iterable)` check (which only checks the type) but
np.iterable() more correctly returns False because it actually tries to
iter on it.
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -1,4 +1,3 @@
-import collections.abc
 import functools
 import itertools
 import logging
@@ -4210,7 +4209,7 @@ def _parse_scatter_color_args(c, edgecolors, kwargs, xsize,
                  else get_next_color_func())
         c_is_string_or_strings = (
             isinstance(c, str)
-            or (isinstance(c, collections.abc.Iterable) and len(c) > 0
+            or (np.iterable(c) and len(c) > 0
                 and isinstance(cbook.safe_first_element(c), str)))
 
         def invalid_shape_exception(csize, xsize):
@@ -4244,7 +4243,7 @@ def invalid_shape_exception(csize, xsize):
         if not c_is_mapped:
             try:  # Is 'c' acceptable as PathCollection facecolors?
                 colors = mcolors.to_rgba_array(c)
-            except ValueError:
+            except (TypeError, ValueError):
                 if not valid_shape:
                     raise invalid_shape_exception(c.size, xsize)
                 # Both the mapping *and* the RGBA conversion failed: pretty
