pytest vs py.test
The Problem¶
pylint installs a pytest script, and pytest installs a py.test script. Confusing.
The pylint code quality checker installs the logilab-common package. logilab-common provides a module called pytest. That’s awfully close to the py.test script that the pytest project provides. I can never remember which one to use, when I have both pylint and pytest installed. Fortunately, the logilab-common package has marked its pytest module as “to be deprecated”, so the confusion might be fixed someday.
Investigating using strace¶
I knew the pytest project was supplying the py.test script, but I did not know where the unwanted pytest script was coming from. strace to the rescue!
$ strace -o trace.txt -e open pytest --help
$ grep pytest trace.txt
open("/home/me/.virtualenvs/dev/bin/pytest", O_RDONLY) = 3
open("/home/me/.virtualenvs/dev/bin/pytest", O_RDONLY) = 3
open("/home/me/.virtualenvs/dev/local/lib/python2.7/site-packages/logilab/common/pytest.x86_64-linux-gnu.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/me/.virtualenvs/dev/local/lib/python2.7/site-packages/logilab/common/pytest.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/me/.virtualenvs/dev/local/lib/python2.7/site-packages/logilab/common/pytestmodule.so", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/home/me/.virtualenvs/dev/local/lib/python2.7/site-packages/logilab/common/pytest.py", O_RDONLY) = 3
open("/home/me/.virtualenvs/dev/local/lib/python2.7/site-packages/logilab/common/pytest.pyc", O_RDONLY) = 4
Here we see that the pytest.py file is in the logilab/common directory, so we know what package installed it.
For a fun intro to strace, see Julia Evans’ strace zine.