{"id":67306,"date":"2022-09-19T09:01:06","date_gmt":"2022-09-19T09:01:06","guid":{"rendered":"https:\/\/www.cryptocabaret.com\/?p=67306"},"modified":"2022-09-19T09:01:06","modified_gmt":"2022-09-19T09:01:06","slug":"pylint-the-good-the-bad-and-the-ugly","status":"publish","type":"post","link":"https:\/\/www.cryptocabaret.com\/?p=67306","title":{"rendered":"PyLint: The good, the bad, and the ugly"},"content":{"rendered":"

PyLint: The good, the bad, and the ugly<\/span>
\nMoshe Zadka<\/a><\/span>
\nMon, 09\/19\/2022 – 03:00<\/span><\/p>\n

\n

Hot take: PyLint is actually good!<\/p>\n

“PyLint can save your life” is an exaggeration, but not as much as you might think! PyLint can keep you from really really hard to find and complicated bugs. At worst, it can save you the time of a test run. At best, it can help you avoid complicated production mistakes.<\/p>\n

The good<\/h2>\n

I’m embarrassed to say how common this can be. Naming tests is perpetually weird<\/em>: Nothing cares about the name, and there’s often not a natural name to be found. For instance, look at this code:<\/p>\n

\n
def<\/span> test_add_small(<\/span>)<\/span>:
\n\u00a0 \u00a0 # Math, am I right?<\/span>
\n\u00a0 \u00a0 assert<\/span> 1<\/span> + 1<\/span> ==<\/span> 3<\/span>
\n\u00a0 \u00a0 
def<\/span> test_add_large(<\/span>)<\/span>:
\n\u00a0 \u00a0 assert<\/span> 5<\/span> + 6<\/span> ==<\/span> 11<\/span>
\n\u00a0 \u00a0 
def<\/span> test_add_small(<\/span>)<\/span>:
\n\u00a0 \u00a0 assert<\/span> 1<\/span> + 10<\/span> ==<\/span> 11<\/span><\/div><\/div><\/pre>\n
The test works:<\/p>\n
\n
collected 2<\/span> items \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 
test<\/span>.py<\/span> .. 
2<\/span> passed <\/div><\/div><\/pre>\n<\/p>\n
\n
More Python resources<\/div>\n
\n
What is an IDE?<\/a><\/div>\n
Cheat sheet: Python 3.7 for beginners<\/a><\/div>\n
Top Python GUI frameworks<\/a><\/div>\n
Download: 7 essential PyPI libraries<\/a><\/div>\n
Red Hat Developers<\/a><\/div>\n
Latest Python articles<\/a><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
But here’s the kicker: If you override a name, the testing infrastructure happily skips over the test!<\/p>\n
In reality, these files can be hundreds of lines long, and the person adding the new test might not be aware of all the names. Unless someone is looking at test output carefully, everything looks fine.<\/p>\n
Worst of all, the addition of the overriding test<\/em>, the breakage of the overridden test<\/em>, and the problem that results in prod<\/em> might be separated by days, months, or even years.<\/p>\n
PyLint finds it<\/h2>\n
But like a good friend, PyLint is there for you.<\/p>\n
\n
test<\/span>.py<\/span>:8<\/span>:0<\/span>: E0102: function already defined line 1<\/span>
\n\u00a0 \u00a0 \u00a0(<\/span>function-redefined)<\/span><\/div><\/div><\/pre>\n
The bad<\/h2>\n
Like a 90s sitcom, the more you get into PyLint, the more it becomes problematic. This is completely reasonable code for an inventory modeling program:<\/p>\n
\n
\"\"\"Inventory abstractions\"\"\"<\/span>

import<\/span> attrs

@<\/span>attrs.define<\/span>
class<\/span> Laptop:
\n\u00a0 \u00a0 \"\"\"A laptop\"\"\"<\/span>
\n\u00a0 \u00a0 ident: str<\/span>
\n\u00a0 \u00a0 cpu: str<\/span><\/div><\/div><\/pre>\n
It seems that PyLint has opinions (probably formed in the 90s) and is not afraid to state them as facts:<\/p>\n
\n
$ pylint laptop.py<\/span> | sed -n '\/^laptop\/s\/[^ ]*: \/\/p'<\/span>
\nR0903: Too few public methods (<\/span>0<\/span>\/2<\/span>)<\/span> (<\/span>too-few-public-methods)<\/span><\/div><\/div><\/pre>\n
The ugly<\/h2>\n
Ever wanted to add your own unvetted opinion to a tool used by millions? PyLint has 12 million monthly downloads.<\/p>\n
\n
“People will just disable the whole check if it’s too picky.” \u2014PyLint issue 6987, July 3rd, 2022<\/p>\n<\/blockquote>\n
The attitude it takes towards adding a test with potentially many false positives is…“eh.”<\/em><\/p>\n
Making it work for you<\/h2>\n
PyLint is fine, but you need to interact with it carefully. Here are the three things I recommend to make PyLint work for you.<\/p>\n
1. Pin it<\/h3>\n
Pin the PyLint version you use to avoid any surprises!<\/p>\n
In your .toml<\/code> file:<\/p>\n
\n
[<\/span>project.optional-dependencies]<\/span><\/span>
pylint<\/span> =<\/span> [<\/span><\/span>\"pylint\"<\/span>]<\/span><\/div><\/div><\/pre>\n
In your code:<\/p>\n
\nfrom<\/span> unittest<\/span> import<\/span> mock<\/code><\/span><\/pre>\n
This corresponds with code like this:<\/p>\n
\n
# noxfile.py<\/span>
\n...
@<\/span>nox.session<\/span>(<\/span>python=<\/span>VERSIONS[<\/span>-1<\/span>]<\/span>)<\/span>
def<\/span> refresh_deps(<\/span>session)<\/span>:
\n\u00a0 \u00a0 \"\"\"Refresh the requirements-*.txt files\"\"\"<\/span>
\n\u00a0 \u00a0 session.install<\/span>(<\/span>\"pip-tools\"<\/span>)<\/span>
\n\u00a0 \u00a0 for<\/span> deps in<\/span> [<\/span>...,<\/span> \"pylint\"<\/span>]<\/span>:
\n\u00a0 \u00a0 \u00a0 \u00a0 session.run<\/span>(<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \"pip-compile\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \"--extra\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 deps,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \"pyproject.toml\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \"--output-file\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 f\"requirements-{deps}.txt\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 )<\/span><\/div><\/div><\/pre>\n
2. Default deny<\/h3>\n
Disable all checks. Then enable ones that you think have a high value-to-false-positive ratio. (Not just false-negative-to-false-positive ratio!)<\/p>\n
\n
# noxfile.py<\/span>
\n...
@<\/span>nox.session<\/span>(<\/span>python=<\/span>\"3.10\"<\/span>)<\/span>
def<\/span> lint(<\/span>session)<\/span>:
\n\u00a0 \u00a0 files =<\/span> [<\/span>\"src\/\"<\/span>,<\/span> \"noxfile.py\"<\/span>]<\/span>
\n\u00a0 \u00a0 session.install<\/span>(<\/span>\"-r\"<\/span>,<\/span> \"requirements-pylint.txt\"<\/span>)<\/span>
\n\u00a0 \u00a0 session.install<\/span>(<\/span>\"-e\"<\/span>,<\/span> \".\"<\/span>)<\/span>
\n\u00a0 \u00a0 session.run<\/span>(<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \"pylint\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \"--disable=all\"<\/span>,<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 *(<\/span>f\"--enable={checker}\"<\/span> for<\/span> checker in<\/span> checkers)<\/span>
\n\u00a0 \u00a0 \u00a0 \u00a0 \"src\"<\/span>,<\/span>
\n\u00a0 \u00a0 )<\/span><\/div><\/div><\/pre>\n
3. Checkers<\/h3>\n
These are some of the ones I like. Enforce consistency in the project, avoid some obvious mistakes.<\/p>\n
\n
checkers =<\/span> [<\/span>
\n\u00a0 \u00a0 \"missing-class-docstring\"<\/span>,<\/span>
\n\u00a0 \u00a0 \"missing-function-docstring\"<\/span>,<\/span>
\n\u00a0 \u00a0 \"missing-module-docstring\"<\/span>,<\/span>
\n\u00a0 \u00a0 \"function-redefined\"<\/span>,<\/span>
]<\/span><\/div><\/div><\/pre>\n
Using PyLint<\/h2>\n
You can take just the good parts of PyLint. Run it in CI to keep consistency, and use the highest value checkers.<\/p>\n
Lose the bad parts: Default deny checkers.<\/p>\n
Avoid the ugly parts: Pin the version to avoid surprises.<\/p>\n<\/div>\n
\n
Get the most out of PyLint.<\/p>\n<\/div>\n
\n
\n
  \"Python<\/div>\n
Image by: <\/span><\/p>\n
Opensource.com<\/p>\n<\/div>\n<\/article>\n<\/div>\n
\n
Python<\/a><\/div>\n<\/p><\/div>\n
What to read next<\/div>\n

\n        \"Creative<\/a>This work is licensed under a Creative Commons Attribution-Share Alike 4.0 International License.<\/div>\n
\n
\n
Register<\/a> or Login<\/a> to post a comment.<\/div>\n<\/p><\/div>\n<\/section>\n
Powered by WPeMatico<\/a><\/small><\/p>\n","protected":false},"excerpt":{"rendered":"
PyLint: The good, the bad, and the ugly Moshe Zadka Mon, 09\/19\/2022 – 03:00 Hot take: PyLint is actually good! “PyLint can save your life” is an exaggeration, but not as much as you might think! PyLint can keep you from really really hard to find and complicated bugs. At worst, it can save you […]<\/p>\n","protected":false},"author":1,"featured_media":67307,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[307],"tags":[],"class_list":["post-67306","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-open-source"],"_links":{"self":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts\/67306","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=67306"}],"version-history":[{"count":0,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/posts\/67306\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=\/wp\/v2\/media\/67307"}],"wp:attachment":[{"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=67306"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=67306"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.cryptocabaret.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=67306"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}