[bug] matplotlib broke compatibility with get_cmap in version 3.9

[lparolari]

I'm reporting a bug encountered during the usage of vot toolkit.

To reproduce

1. Install vot-toolkit (pip install vot-toolkit)
2. Run vot initialize vot2022 --workspace workspace

It raises the following error

cannot import name 'get_cmap' from 'matplotlib.cm'

I'm using python 3.10.

About the error

The get_cmap function is used here: https://github.com/votchallenge/toolkit/blob/0abc8e537ca8c94bf898abae0217529daa272e7d/vot/report/__init__.py#L305

I did some digging on the internet and I found it is a recent change introduced by matplotlib in version3.9. Here I report the 3.9 changelog that removed get_cmap function: https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.9.0.html#top-level-cmap-registration-and-access-functions-in-mpl-cm

Other projects are having the same issue:

• https://github.com/haranjackson/PyPDE/issues/3
• https://github.com/atarashansky/SAMap/issues/148

Possible solutions

• (workaround) Downgrade matplotlib to 3.8
• Upgrade the usage according to new API. The changelog says:

use matplotlib.colormaps[name] instead if you have a str. Use matplotlib.cm.ColormapRegistry.get_cmap if you have a str, None or a matplotlib.colors.Colormap object that you want to convert to a Colormap object.

I am willing to investigate more on the problem and possibly fix the code. Guidance might help.

Thank you

[lukacu]

I have committed to fixing this issue in the development branch.

[lparolari]

Thank you