CODEWITHSUNDEEP
python
TheSoundDefense
TheSoundDefense

Reputation: 6945

Testing all functions in a module for errors

This may be a dumb question, but charging boldly ahead anyway.

I have a library of about a dozen Python modules I maintain for general use. Recently, after advice found here on SO, I changed all of the modules so they are imported in the import x as y style instead of from x import *. This solved several problems and made the code easier to manage.

However, there was an unintended side effect of this. Many of the modules use Python builtin modules like sys or os to do whatever, and the way the code was previously set up, if I typed import sys in module x, and used from x import * in module y, I didn't have to import sys in module y. As a result, I took this for granted quite a lot (terrible practice, I know). When I switched to import x, this caused a lot of broken functions, as you can imagine.

So here's the main issue: because Python is an interpreted language, errors about missing modules in a function won't show up until a function is actually run. And because this is just a general-use library, some of these errors could persist for months undetected, or longer.

I'm completely prepared to write a unit test for each module (if __name__ == "__main__" and all that), but I wanted to ask first: is there an automated way of checking every function in a module for import/syntax errors, or any other error that is not dependent on input? Things that a compiler would catch in C or another language. A brief Google and SO search didn't turn up anything. Any suggestions are welcome and appreciated.

Upvotes: 2

Views: 123

Answers (1)

Lukas Graf
Lukas Graf

Reputation: 32610

Yes. PyFlakes will warn you about those most basic errors, and you should make sure it's integrated with your favorite text editor, so it tells you about missing imports or unused imports whenever you save the file.

PyFlakes will, amgonst other things, tell you about

  • syntax errors
  • undefined names
  • missing imports
  • unused imports

To just run PyFlakes on all your files in a directory, you can just do:

pyflakes /path/to/dir

One big advantage that PyFlakes has over more advanced linting tools like PyLint is that it does static analysis - which means, it doesn't need to import your code (which can be a pain if you've got some complex dependencies). It just analyses the abstract syntax tree of your Python source, and therefore catches the most basic of errors - those that usually prevent your script from having even a chance of running.

I should also mention that there is a related tool, flake8, which combines PyFlakes with PEP8 convention checks and McCabe code complexity analysis.

There's PyFlakes integrations for every editor (or IDE) I know. Here's just a couple (in no particular order):

Upvotes: 2

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