Problem

Recently I wanted to draw some colormapped vlines. As LineCollection inherits from ScalarMappable, one can indeed write e.g.

from pylab import *
xs = vals = np.arange(10)
plt.vlines(xs, 0, 1, array=vals)
plt.show()

and get

Unfortunately,

1. The array kwarg only accepts ndarrays, and not e.g. nested lists: plt.vlines(np.arange(10), 0, 1, array=[*range(10)]) crashes (at draw time, which is even worse) with "AttributeError: 'list' object has no attribute 'ndim'". This is unlike most other Axes/pyplot APIs (e.g. imshow), which happily accept lists (nested/2D lists, for imshow).
2. The array kwarg is not copied, so later changes to it get reflected back into the artist (i.e. doing vals[5] = 45 after the call to vlines still affects the line colors). Again, this is unlike other Axes/pyplot APIs (e.g. imshow), which insulate the artist from later changes to the input.

Proposed Solution

Make a copy of the input and cast it to arrays. (Well, modulo unit handling...)

Additional context and prior art

Behave like imshow.