DOC matplotlib versus matplotlib-base

[beckermr]

We recently ran into this with pystan: conda-forge/pystan-feedstock#27

Apparently, it is sometimes preferable to depend only on matplotlib-base. We might want to add a section to the special dependencies describing when and why.

@maresb has more details I think

[beckermr]

See also this issue: jupyter/docker-stacks#896 (comment)

[maresb]

Thanks @beckermr for bringing this up here. I don't have much to add beyond what's in the comment linked above.

Whenever I personally conda install a package which requires matplotlib instead of matplotlib-base, I have been submitting a pull request to the corresponding feedstock. I could imagine that in 99% of the cases where a package requires matplotlib it is more appropriate to require matplotlib-base. This makes me wonder if it would be sensible to somehow make a bulk pull request to all (active) feedstocks which require matplotlib to switch over to matplotlib-base. (Or simply to remove pyqt from matplotlib.) I'm relatively new here, so I don't understand the design decisions.

[beckermr]

So the only difference is whether or not a functional backend (pyqt) is installed too?

We can make bulk PRs via a special migration using the conda-forge bots if we think it is appropriate.

What happens in an env where only matplotlib-base is installed and someone tries to use matplotlib?

[maresb]

I use JupyterLab as my backend, and matplotlib (installed as matplotlib-base) runs perfectly fine without having qt/pyqt installed.

[beckermr]

OK. I did some testing on a linux box and on my mac. Without pyqt, everything appears to work out of the box.

I am confused on one thing though. On linux, it appears that matplotlib-base is shipping the tk backend already

Python 3.7.3 | packaged by conda-forge | (default, Jul  1 2019, 21:52:21) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import matplotlib.pyplot as plt
>>> plt.plot(list(range(10)))
[<matplotlib.lines.Line2D object at 0x7f4cc9754d30>]
>>> plt.show()
>>> plt.get_backend()
'TkAgg'
>>> exit()
(test-mpl) [beckermr@astro0010 ~]$ conda list
# packages in environment at /gpfs02/astro/workarea/beckermr/miniconda3/envs/test-mpl:
#
# Name                    Version                   Build  Channel
_libgcc_mutex             0.1                        main  
bzip2                     1.0.8                h516909a_1    conda-forge
ca-certificates           2019.9.11            hecc5488_0    conda-forge
certifi                   2019.9.11                py37_0    conda-forge
cycler                    0.10.0                     py_2    conda-forge
freetype                  2.10.0               he983fc9_1    conda-forge
icu                       64.2                 he1b5a44_1    conda-forge
kiwisolver                1.1.0            py37hc9558a2_0    conda-forge
libblas                   3.8.0               14_openblas    conda-forge
libcblas                  3.8.0               14_openblas    conda-forge
libffi                    3.2.1             he1b5a44_1006    conda-forge
libgcc-ng                 9.1.0                hdf63c60_0  
libgfortran-ng            7.3.0                hdf63c60_2    conda-forge
liblapack                 3.8.0               14_openblas    conda-forge
libopenblas               0.3.7                h6e990d7_3    conda-forge
libpng                    1.6.37               hed695b0_0    conda-forge
libstdcxx-ng              9.1.0                hdf63c60_0  
matplotlib-base           3.1.2            py37h250f245_1    conda-forge
ncurses                   6.1               hf484d3e_1002    conda-forge
numpy                     1.17.3           py37h95a1406_0    conda-forge
openssl                   1.1.1d               h516909a_0    conda-forge
pip                       19.3.1                   py37_0    conda-forge
pyparsing                 2.4.5                      py_0    conda-forge
python                    3.7.3                h33d41f4_1    conda-forge
python-dateutil           2.8.1                      py_0    conda-forge
readline                  8.0                  hf8c457e_0    conda-forge
setuptools                42.0.1                   py37_0    conda-forge
six                       1.13.0                   py37_0    conda-forge
sqlite                    3.30.1               hcee41ef_0    conda-forge
tk                        8.6.10               hed695b0_0    conda-forge
tornado                   6.0.3            py37h516909a_0    conda-forge
wheel                     0.33.6                   py37_0    conda-forge
xz                        5.2.4             h14c3975_1001    conda-forge
zlib                      1.2.11            h516909a_1006    conda-forge

Does this need to be separated out like the qt backend?

@conda-forge/matplotlib for viz and insight

[dopplershift]

Technically speaking, the matplotlib-base package ships the code for all backends. The matplotlib package does not actually ship any files, all it does is depend on matplotlib-base and pyqt. Matplotlib as of v3.0 (and I think back-ported to 2.2.3) does only run-time detection of backends based on available libraries.

I'm not sure why matplotlib-base depends on tk and only on linux. As I understand it, though, that's effectively harmless as tk is required for Python on Mac and Linux.

[jjhelmus]

The python conda package depends on tk (except on Windows where it is vendored) as it is needed for the tkinter module in the standard library. Even if matplotlib-base dropped the dependency on tk it will still be installed unless one is using a custom built python package.

[beckermr]

OK. So blanket instructions that dependencies on matplotlib should be on matplotlib-base seems like it would be fine on all platforms?

[dopplershift]

I think that would be fair.

[beckermr]

I added docs. We might consider both a migrator and a PR on the linter. I will make issues for those.

[beckermr]

OK. This is 503 packages, so we def need a migrator if we want it.