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flake8-blind-except

A flake8 extension that checks for blind, catch-all except: and except Exception: statements.

As of pycodestyle 2.1.0, "E722 do not use bare except, specify exception instead" is built-in. However, bare Exception and BaseException are still allowed. This extension flags them as B902.

Using except without explicitly specifying which exceptions to catch is generally considered bad practice, since it catches system signals like SIGINT. You probably want to handle system interrupts differently than exceptions occurring in your code.

It's also usually better style to have many small try-except blocks catching specific exceptions instead of a giant try: block with a catch-all except: at the bottom. It's also nicer to your fellow programmers to be a bit more specific about what exceptions they can expect in specific parts of the code, and what the proper course of action is when they occur.

An example of code that will fail this check is:

try:
    something_scary()
except:
    everybody_panic()

However, the following code is valid:

try:
    something_terrifying()
except TerrifyingException:
    dont_panic()

Installation

If you don't already have it, install flake8:

$ pip install flake8

Then, install the extension:

$ pip install flake8-blind-except

Usage

Run the following to verify that the plugin has been installed correctly:

$ flake8 --version
2.0 (pep8: 1.4.6, flake8-blind-except: 0.1.0, pyflakes: 0.7.3)

Now, when you run flake8, the plugin will automatically be used.

When a blind except is found, flake8 will output:

B901 blind except: statement

or:

B902 blind except Exception: statement

Contributing

I'm not working on Python these days, so probably won't be making updates anytime soon. PRs are welcome though!

Testing

Tests can be run with pytest --doctest-modules flake8_blind_except.py.

Changes

0.2.1 - 2022-03-08

  • Remove setuptools from install_requires (#8)

0.2.0 - 2021-01-07

  • B902 error added for cases where a blind Exception is caught.

0.1.1 - 2016-06-27

  • pep8 was renamed to pycodestyle in its 2.0 release. Compatibility update for this change.

0.1.0 - 2014-02-07

  • Initial release

Notes

I've tested this package with flake8 2.6.2 + Python 2.7.3 and flake8 3.7.9 + Python 3.7.5.