Mailman 3 December 2014 - code-quality

check for files with bad styles
by Juan BC 12 Dec '14

12 Dec '14

i actually writing a test case who check code style with flake8 i interested in retrieve only the name of the files with errors not the error itself, so after some research i trying to capture the stdout of flake8 and write the next code out, err = sys.stdout, sys.stderr dummy = StringIO() sys.stdout, sys.stderr = dummy, dummy pep8 = engine.get_style_guide() pep8.paths = [....] report = pep8.check_files() sys.stdout, sys.stderr = out, err Always dummy.getvalue() comes empty. Its another way to retrieve the list of files who fail the check? also i try to write my own report class who inherit from BaseQReport and add redefining a error method with a multiprocessing.Queue for communication but don't work Sorry for my poor english grammar regards.

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The union of all tools
by Skip Montanaro 09 Dec '14

09 Dec '14

Thinking about the discussion I (inadvertently) started about what sorts of issues should cause tools like pylint and pyflakes to emit messages, got me thinking about how I try to use these tools. I don't know what the current suite of all available static checking tools is, but let me just assume for the moment that we have three tools: pylint, pyflakes, and (the probably now defunct) pychecker. Each one has different goals, which naturally affects the messages it can possibly emit. For example, because pychecker imports the modules mentioned in the code it analyzes, it is able to build symbol tables for extension modules. OTOH, it could be slower, the user might suffer if importing modules had side effects, and to get the most out of it, you were tied to the platforms for which you had compiled extension modules. I don't think pylint actually imports the code it analyzes, so it can be more platform-independent, but not as comprehensive as pychecker when trying to emit warnings about cross-module issues. It can, however, identify other problematic constructs. As a user of these tools, recognizing that none will ever be "complete", I try to use multiple tools precisely so I can see the union of all messages. In fact, some while ago (at least a couple years, probably longer), I wrote a shell script wrapper which invokes both pychecker and pylint, presenting me with the sorted (and very lightly massaged) output. If pyflakes is so conservative in what it will emit that it tries to avoid all possible false positives, it's less useful to me, precisely because the odds are low that it will report problems the other available tools won't catch. That is: pylint ∪ pychecker ≈ pylint ∪ pychecker ∪ pyflakes making the incremental benefit to me of using pyflakes small. This is not to say that Phil doesn't have excellent reasons for his approach, just that there is a non-trivial trade-off in that approach. Skip

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Time cost for pylint analyses?
by Anne Mulhern 08 Dec '14

08 Dec '14

Hi! Would it be possible to be able to extend pylint somehow to record a time cost for individual pylint analyses? - mulhern

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This seems like a good warning candidate...
by Skip Montanaro 08 Dec '14

08 Dec '14

I just bumped into a bug, reusing the same loop variable in two nested for loops. Here's an example: def f(x): for i in range(x): for i in [1, 2, 3]: print i Neither pylint nor flake8 warned about this problematic usage. Had i or x shadowed a global of the same name, pylint would have complained, e.g.: x = 7 def f(x): for i in range(x): for i in [1, 2, 3]: x = i print i, x Using the same variable in nested loops within the same function seems at least as serious as a shadowed global (or builtin) name. Skip

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Advice regarding caching values as a side-effect of visiting classes
by Anne Mulhern 04 Dec '14

04 Dec '14

Hi! I've implemented a very simple analysis of the kind described in this enhancement request: https://bitbucket.org/logilab/pylint/issue/201/pointless-attribute-override…. The analysis is neither sound nor complete, but has proven useful for removing of bits of dead code. It can be made more sound by altering the algorithm so that it accumulates data by visiting classes, and subsequently processes that accumulated data, preferably after all classes have been visited, in order to determine messages to report. Is there some infrastructure in pylint that can accomodate an analysis that works that way? If there is, is there a working example that uses it? Thanks for any help, - mulhern

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