Remove stale bytecode files

[pytestbot]

Originally reported by: Wolfgang Schnerring (BitBucket: wosc, GitHub: wosc)

---

The situation is rather rare (when switching between branches for example) that you get obsolete .pyc/.pyo files, i.e. without corresponding .py files, but when it occurs it can lead to obscure and really hard to detect problems. So it might be a worthwile feature to clean those up automatically (zope.testrunner does this for example).

---

• Bitbucket: https://bitbucket.org/pytest-dev/pytest/issue/590

[pytestbot]

Original comment by Michael Howitz (BitBucket: icemac, GitHub: icemac):

---

We developed a plug-in which removes stale byte code files: https://pypi.python.org/pypi/pytest-remove-stale-bytecode

So the ticket an be considered as solved.

[pytestbot]

Original comment by Floris Bruynooghe (BitBucket: flub, GitHub: flub):

---

Thanks, a plugin seems like a nice solution. If it turns out very popular it can always be included in the core.

[pytestbot]

Original comment by BitBucket: faassen, GitHub: faassen:

---

I just came here to report that this would be a useful feature to me too.

Is there a good reason for py.test not to do this by default?

[pytestbot]

Original comment by holger krekel (BitBucket: hpk42, GitHub: hpk42):

---

So far i didn't see it as a core responsibility of a testing tool to clean up pyc files. Personally i use py.cleanup from the pycmd package and i think the plugin posted here is also a good idea. Maybe it could just be named "pytest-nopyc" though to make it easier to install out of the head :)

[pytestbot]

Original comment by BitBucket: faassen, GitHub: faassen:

---

The argument for making it the responsibility of the test runner is because it can lead to correctly written tests passing that shouldn't be failing, without warning.

It's tripped me up quite a few times after I started using py.test and it never did with the zope test runner. It sometimes takes a little bit of time to realize what is going on, sometimes after pushing the code, and sometimes until I check out the code again. It's never a huge deal, but it just happened to come up again (in the context of nose, actually) and I figured this time I'd say something. Just that little bit of extra usability that I've come to expect from py.test.

A warning would be an alternative: "this test only works because there's a .pyc file without .py file". Or maybe "stale .pyc files detected".

[pytestbot]

Original comment by Markus Unterwaditzer (BitBucket: untitaker, GitHub: untitaker):

---

I think this behavior should be added to tox instead, because tox already takes precautions like setting the PYTHONHASHSEED.

[pytestbot]

Original comment by BitBucket: faassen, GitHub: faassen:

---

Maybe tox should also do something, but I run into this when I use pytest alone. (with tox I frequently need to nuke the .tox directory to make things go again, but I haven't dug into why this is yet)

[pytestbot]

Original comment by Floris Bruynooghe (BitBucket: flub, GitHub: flub):

---

Is this something that affects both Python 2.x and 3.x or just 2.x? My own quick experimentation makes me think this only affects 2.x.