Conflicting dependencies when installing via pip (Cartopy) about xmovie HOT 4 OPEN

Hi @jbusecke. Yes, a pure conda installation works fine, even when cartopy=0.20 is installed (which looks like being the source of the reported issue with pip). The following command correctly installs xmovie with cartopy=0.20.2 and proj=9.0.0:

conda create --override-channels -c anaconda -c conda-forge -n xmovie python=3.9 xmovie

from xmovie.

Fix

conda environment

Install proj from conda-forge prior installing xmovie:

conda create -n xmovie python=3.9
conda activate xmovie
conda install -c conda-forge proj
pip install xmovie

venv environment

Install version cartopy==0.19.0.post1 before installing xmovie (see SciTools/iris#4468 (comment))

python3 -m venv venv
source venv/bin/activate
pip install cartopy==0.19.0.post1
pip install xmovie

from xmovie.

Thanks for reporting this problem @mcucchi9. This is certainly frustrating.
Does a conda only install e.g. conda create -n xmovie python=3.9 xmovie work for you? I have had some issues with cartopy dependencies via pip in other contexts lately.
I am however not quite sure how to fix this. If the above works, I could add appropriate warnings to the readme/docs, but it would be nice to find a more elegant solution for this.

from xmovie.

Would it be possible to make cartopy as an optional dependency?

Context: We use xarray in the library pymech and snek5000 and we would like to try out xmovie (snek5000/snek5000#118). We do not foresee the use of cartopy in those packages and IIRC, it can be notoriously difficult to install without conda.

from xmovie.