Matplotlib import error

Part 1 (2018)
1

I am trying to run fastai on a local machine (Mac notebook), and I get an error with Lesson 5 that reads…

—> 46 from matplotlib import (
47 backend_tools as tools, cbook, colors, textpath, tight_bbox, transforms,
48 widgets, get_backend, is_interactive, rcParams)

ImportError: cannot import name ‘get_backend’

I am using Anaconda and have a fastai environment (also a fastai-cpu environment, since Apple has not released an updated CUDA driver for 5 months(!!!)). My python environment works in general, except for this error. I’m pretty new to Python and environments and haven’t been able to figure out how to fix it.

Thanks!
John

2

Answering my own question; it turned out to be my confusion over Python environments. Some of the packages that fastai was looking for were in the fastai-cpu environment, not the fastai environment. I discovered that by dumping the contents of each environment into a .yml file and then comparing them-- a handy trick since I wanted to see the contents side by side:
conda activate fastai-cpu
conda env export > fastai-cpu_env.yml
…for each environment. There’s probably a simpler way.
I was also using Jupyter Lab, which I really love (it’s a much-improved alpha version of Jupyter Notebooks with a lot of really nice features – see this intro and I had installed that in my (base) conda environment, without really realizing that. So to correct the problem, I did this:

  1. Added Jupyter Lab to the fastai-cpu environment:
    conda install -n fastai-cpu -c conda-forge jupyterlab

  2. Now whenever I start it up, I just have to remember to switch to fastai-cpu:
    conda activate fastai-cpu
    jupyter lab
    …and it all works.