BUG: plot with kind=scatter fails when checking if an array is in the DataFrame

[TomAugspurger]

df = pd.DataFrame({'A': [1, 2], 'B': [3, 4]})
c = np.array([1, 0])
df.plot(kind='scatter', x='A', y='B', c=c, cmap='spring')

fails with a TypeError.

we check elif c in self.data.columns which tries to hash the array.

(I know I can just add the array as a column to the DataFrame)

[jorisvandenbossche]

How should this supposed to work in this case? The length of the array is not equal to the number of elements in the dataframe?

[shoyer]

@jorisvandenbossche c = np.array([1, 0]) also raises.

[jorisvandenbossche]

@shoyer yes, OK, I just found it a bit strange example (as this would have failed with matplotlib also)

I suppose this is related to #7780, and apparantly this case wasn't catched by the tests? So it seems a regression from 0.14

[shoyer]

@jorisvandenbossche Yes, this is a regression (and I introduced it in #7780). If nobody else gets to it first I can write a fix (should be pretty easy).

[TomAugspurger]

@jorisvandenbossche sorry about the bad example! I meant to have c=[1, 0]. My excuse is that I'm on a Windows PC right now and copy-pasting from the interpreter is a pain.

[jorisvandenbossche]

@TomAugspurger right-clicking with the mouse?

[TomAugspurger]

Wow, that is not at all obvious that that puts it on your clipboard :) Thanks.

[jorisvandenbossche]

Yep, indeed, it also took me a while to know this.. But now rather essential when I am working on Windows

[jorisvandenbossche]

@jreback What is actually the best way to check if something is allowed to be a column name?

elif c in self.data.columns gives an error with np.arrays eg, but how to check for this?