clean code

[joamatab]

Simplify meep code

• Replace if statement with if expression (assign-if-exp)
• Convert for loop into list comprehension (list-comprehension)
• use fstrings
• add pre-commit hook
• format code with black

[joamatab]

#2163

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[stevengj]

It would be good to figure out how to cleanly rebase existing PRs after this is merged, maybe similar to the instructions in #662.

For example, if you could try rebasing #1951 that would be helpful.

[codecov-commenter]

Codecov Report

Merging #2164 (83dc114) into master (5cb0311) will increase coverage by 0.22%.
The diff coverage is 60.78%.

@@            Coverage Diff             @@
##           master    #2164      +/-   ##
==========================================
+ Coverage   73.07%   73.29%   +0.22%     
==========================================
  Files          17       17              
  Lines        4951     4891      -60     
==========================================
- Hits         3618     3585      -33     
+ Misses       1333     1306      -27     

Impacted Files	Coverage Δ
python/simulation.py	76.95% <ø> (+0.01%)	⬆️
python/source.py	95.31% <ø> (-0.15%)	⬇️
python/timing_measurements.py	92.50% <ø> (-0.36%)	⬇️
python/verbosity_mgr.py	66.66% <ø> (-7.91%)	⬇️
python/visualization.py	43.40% <ø> (+0.44%)	⬆️
python/adjoint/connectivity.py	10.47% <5.26%> (+0.38%)	⬆️
python/adjoint/basis.py	16.10% <12.00%> (+0.39%)	⬆️
python/adjoint/optimization_problem.py	56.84% <40.81%> (+2.16%)	⬆️
python/adjoint/filters.py	60.86% <60.86%> (+0.30%)	⬆️
python/adjoint/filter_source.py	88.46% <78.57%> (ø)
... and 12 more

[stevengj]

CI failure for tests/test_material_grid.py & some other tests … seems to be a failure to import the adjoint module, probably due to import re-ordering.

[stevengj]

Instructions for rebasing other branches after this PR:

Replace MYBRANCH below with the name of your branch:

# update repo
git checkout master && git pull origin master # update master

# switch to your branch
git checkout MYBRANCH

# rebase onto PREVIOUS commit
git rebase c49efbeee91d1de26f86e207d921dfd9fc3680d4

# grab the pre-commit script and install pre-commit
curl https://raw.githubusercontent.com/NanoComp/meep/55f909d11ce671ca762999d5eae55e5c8e9304f2/.pre-commit-config.yaml > .pre-commit-config.yaml
pip3 install pre-commit
pre-commit install

# reformat and rebase to THIS PR's commit
git commit -a -m "reformat"
rm  .pre-commit-config.yaml
git rebase -Xtheirs b00f2d4ce20e683275a4895c8dc8318677a296d1

# finish rebase
git rebase master