flake8-bugbear

A plugin for flake8 finding likely bugs and design problems in your program. Contains warnings that don't belong in pyflakes and pycodestyle:

bug·bear  (bŭg′bâr′)
n.
1. A cause of fear, anxiety, or irritation: *Overcrowding is often
   a bugbear for train commuters.*
2. A difficult or persistent problem: *"One of the major bugbears of
   traditional AI is the difficulty of programming computers to
   recognize that different but similar objects are instances of the
   same type of thing" (Jack Copeland).*
3. A fearsome imaginary creature, especially one evoked to frighten
   children.

List of warnings

B001: Do not use bare except:, it also catches unexpected events like memory errors, interrupts, system exit, and so on. Prefer except Exception:. If you're sure what you're doing, be explicit and write except BaseException:.

B002: Python does not support the unary prefix increment. Writing ++n is equivalent to +(+(n)), which equals n. You meant n += 1.

B003: Assigning to os.environ doesn't clear the environment. Subprocesses are going to see outdated variables, in disagreement with the current process. Use os.environ.clear() or the env= argument to Popen.

Python 3 compatibility warnings

These have higher risk of false positives but discover regressions that are dangerous to slip through when test coverage is not great. Let me know if a popular library is triggering any of the following warnings for valid code.

B301: Python 3 does not include .iter* methods on dictionaries. The default behavior is to return iterables. Simply remove the iter prefix from the method. For Python 2 compatibility, also prefer the Python 3 equivalent if you expect that the size of the dict to be small and bounded. The performance regression on Python 2 will be negligible and the code is going to be the clearest. Alternatively, use six.iter* or future.utils.iter*.

B302: Python 3 does not include .view* methods on dictionaries. The default behavior is to return viewables. Simply remove the view prefix from the method. For Python 2 compatibility, also prefer the Python 3 equivalent if you expect that the size of the dict to be small and bounded. The performance regression on Python 2 will be negligible and the code is going to be the clearest. Alternatively, use six.view* or future.utils.view*.

B303: The __metaclass__ attribute on a class definition does nothing on Python 3. Use class MyClass(BaseClass, metaclass=...). For Python 2 compatibility, use six.add_metaclass.

B304: sys.maxint is not a thing on Python 3. Use sys.maxsize.

B305: .next() is not a thing on Python 3. Use the next() builtin. For Python 2 compatibility, use six.next().

B306: BaseException.message has been deprecated as of Python 2.6 and is removed in Python 3. Use str(e) to access the user-readable message. Use e.args to access arguments passed to the exception.

Tests

Just run:

python setup.py test

OMG, this is Python 3 only!

Relax, you can run flake8 with all popular plugins as a tool perfectly fine under Python 3.5+ even if you want to analyze Python 2 code. This way you'll be able to parse all of the new syntax supported on Python 3 but also effectively all the Python 2 syntax at the same time.

If you're still invested in Python 2, there might be a small subset of deprecated syntax that you'd have to abandon... but you're already doing that, right? six or python-future bridge the gaps.

By making the code exclusively Python 3.5+, I'm able to focus on the quality of the checks and re-use all the nice features of the new releases (check out pathlib) instead of wasting cycles on Unicode compatiblity, etc.

License

MIT

Change Log

16.9.0

• introduced B003

16.7.1

• bugfix: don't omit message code in B306's warning
• change dependency on pep8 to dependency on pycodestyle, update flake8 constraint to at least 2.6.2

16.7.0

• introduced B306

16.6.1

• bugfix: don't crash on files with tuple unpacking in class bodies

16.6.0

• introduced B002, B301, B302, B303, B304, and B305

16.4.2

• packaging herp derp

16.4.1

• bugfix: include tests in the source package (to make setup.py test work for everyone)
• bugfix: explicitly open README.rst in UTF-8 in setup.py for systems with other default encodings

16.4.0

• first published version
• date-versioned

Authors

Glued together by Łukasz Langa.