Opened 11 years ago
Closed 8 years ago
#21628 closed Cleanup/optimization (fixed)
Stop using the `imp` module
Reported by: | Aymeric Augustin | Owned by: | nobody |
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Component: | Core (Other) | Version: | dev |
Severity: | Normal | Keywords: | |
Cc: | merb | Triage Stage: | Ready for checkin |
Has patch: | yes | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
It's deprecated in Python 3.4: http://docs.python.org/3.4/library/imp. Django uses it in a handful of files.
Notably, it calls imp.acquire_lock()
and imp.release_lock()
in AppCache.populate()
. These functions don't have a replacement. I'm not sure how to deal with that, maybe call them only on Python < 3.4?
Change History (18)
comment:1 by , 11 years ago
comment:2 by , 11 years ago
As @aaugustin pointed out in a github comment, we used to have normal reentrant threads locking instead of calling these functions and that caused deadlocks (#18251).
It seems the behavior of those functions changed in 3.3 as well, dunno if the change affected us:
"Changed in version 3.3: The locking scheme has changed to per-module locks for the most part. A global import lock is kept for some critical tasks, such as initializing the per-module locks."
FWIW the Python ticket where the deprecation was discussed: http://bugs.python.org/issue17177.
comment:3 by , 11 years ago
@aaugustin i think we could just ignore this issue.
Currently I tried: https://code.djangoproject.com/attachment/ticket/18251/threading_lock.tar.gz
On Python 2.7.5+ and on Python 3.3.2+ the issue never occured. Without calling imp.acquire_lock()
or imp.release_lock()
Maybe the "test" itself is somehow not correct anymore.
But I think its due to the fact that we now (since the last commit https://github.com/django/django/compare/fe1389e911b0...4a56a93cc458) use https://pypi.python.org/pypi/importlib a backport of importlib for python 2.7 due to the fact that the next django version won't be compatible to python 2.6. So just remove imp and we are fine. (btw. imp.acquire_lock() does nothing when you are working on master)
comment:4 by , 11 years ago
Cc: | added |
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comment:6 by , 11 years ago
The app registry no longer uses the import lock, but there's still 5 uses of imp.find_module
, one of imp.load_module
and one of imp.new_module
.
comment:7 by , 11 years ago
It's worth noting that imp.find_module
is the only one of these which is used in the source code (4 times), the others are only used in tests. Two of the uses in the main codebase are in a function which needs rewriting as it's about the old sys.path
hackery from the old project layout, and we've already decided we are willing to *maybe* break some stuff there. There's already a TODO
to this effect.
The others are in module_loading
and we will need to write a separate path for py3+
comment:9 by , 11 years ago
FWIW, the only remaining usage of imp
is in django.utils.module_loading.module_has_submodule
(+ in the corresponding test module, test_module_loading.py
).
comment:11 by , 11 years ago
Removing usage in the tests is quite difficult. I tried to use the replacements from importlib but I keep hitting infinite recursions.
In fact it's a bit difficult to figure out what matters in the test. They were introduced in #13464 but that ticket is short on details.
If I understand Python's deprecation policy correctly, the imp
module won't be removed before Python 4. We could simply silence the deprecation warning.
The alternative would be to run these tests only under Python < 3.3. The implementation on Python >= 3.3 is drastically simpler and may not require as many tests.
comment:12 by , 10 years ago
I think the one remaining case is in ProxyFinder
in tests/utils_tests/test_module_loading.py
comment:13 by , 10 years ago
Another usage popped up:
db/migrations/loader.py: six.moves.reload_module(module)
This uses imp.reload()
on Python 3. It should use importlib.reload()
on Python 3.4+ to avoid a warning. Created ticket to see if it can be addressed in six.
comment:14 by , 10 years ago
Resolution: | → fixed |
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Status: | new → closed |
Issue in previous comment will be fixed in the next version of six. I don't think there are any remaining tasks for this ticket.
comment:15 by , 9 years ago
Resolution: | fixed |
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Status: | closed → new |
Oops, import imp
still exists in tests/utils_tests/test_module_loading.py
.
comment:16 by , 8 years ago
Has patch: | set |
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comment:17 by , 8 years ago
Triage Stage: | Accepted → Ready for checkin |
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We'll most likely have to write some wrappers in django.utils.importlib to cover all Python versions.