[issue17953] sys.modules cannot be reassigned
Eric Snow added the comment: For the record, issue12633 has some more discussion on this. -- nosy: +eric.snow ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Roundup Robot added the comment: New changeset 4f8160e45cb7 by Brett Cannon in branch '3.3': Issue #17953: document that sys.modules shouldn't be replaced (thanks http://hg.python.org/cpython/rev/4f8160e45cb7 New changeset b60ae4ebf981 by Brett Cannon in branch 'default': merge fix for issue #17953 http://hg.python.org/cpython/rev/b60ae4ebf981 -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Brett Cannon added the comment: Thanks for the patch, Yogesh, but I went with different wording that I came up with on the train the other day while offline. But you did remind me to update Misc/NEWS (which led to a discussion on python-committers), so thanks for that. -- resolution: - fixed status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Yogesh Chaudhari added the comment: You are most welcome Brett. I am just starting to contribute with this doc fix. Didn't think a small detail in it will generate such a long debate in the python-committers mailing list. Is there a plan in action for 'fixing' Misc/NEWS. I now realize that this change is too small to warrant an entry there, however, as someone new to the list, I simply followed http://docs.python.org/devguide/patch.html. Doing a make patchcheck warns about no changes to Misc/NEWS. IMHO it would be great if this tool can look at the files changed (or maybe at-least just the directory, or even, simply number of lines modified) and decide if an entry is required in Misc/News. Of-course this is from my perspective. I would like to get your view on this and help about the solution if possible. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
R. David Murray added the comment: I think that is a reasonable suggestion for an enhancement to patchcheck (though I think Brett had a good reason to add a news entry in this particular case). You could open a new issue with that suggestion. On the other hand, patchcheck always warns about other stuff that it can't so easily realize aren't really needed, so it may not be considered a worthwhile enhancement. -- nosy: +r.david.murray ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Yogesh Chaudhari added the comment: That sounds good. I will open up an issue (if not for anything else other than to get more eyes on this issue) -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Yogesh Chaudhari added the comment: Documentation added for sys.modules -- keywords: +patch nosy: +Yogesh.Chaudhari Added file: http://bugs.python.org/file30305/issue17953.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Terry J. Reedy added the comment: sys.modules This is a dictionary that maps module names to modules which have already been loaded. This can be manipulated to force reloading of modules and other tricks. How about adding at the end However, replacing or clearing it may cause Python to fail. or to be slightly more explicit However, replacing it or deleting critical entries may cause Python to fail. -- nosy: +terry.reedy stage: test needed - needs patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Brett Cannon added the comment: Sounds good to me. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
New submission from ProgVal:
In Python 3.3 (I did not test with 3.4), sys.modules cannot be reassigned
without breaking the import mechanism; while it works with Python = 3.2.
Here is how to reproduce the bug:
progval@Andromede:/tmp$ mkdir test_imports
progval@Andromede:/tmp$ echo from . import module test_imports/__init__.py
progval@Andromede:/tmp$ echo print('foo') test_imports/module.py
progval@Andromede:/tmp$ python3.3
Python 3.3.1 (default, Apr 6 2013, 13:58:40)
[GCC 4.7.2] on linux
Type help, copyright, credits or license for more information.
import sys
sys.modules = dict(sys.modules)
import test_imports
Traceback (most recent call last):
File stdin, line 1, in module
File ./test_imports/__init__.py, line 1, in module
from . import module
SystemError: Parent module 'test_imports' not loaded, cannot perform relative
import
progval@Andromede:/tmp$ python3.2
Python 3.2.3 (default, May 6 2013, 01:46:35)
[GCC 4.7.2] on linux2
Type help, copyright, credits or license for more information.
import sys
sys.modules = dict(sys.modules)
import test_imports
foo
--
components: Interpreter Core
messages: 188901
nosy: Valentin.Lorentz
priority: normal
severity: normal
status: open
title: sys.modules cannot be reassigned
type: behavior
versions: Python 3.3
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[issue17953] sys.modules cannot be reassigned
Changes by Christian Heimes li...@cheimes.de: -- assignee: - brett.cannon keywords: +3.3regression nosy: +brett.cannon ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Antoine Pitrou added the comment: I wouldn't call it a bug personally. The modules dictionary is used in all kinds of places in the interpreter; you can change the dictionary's contents, but not swap it with another one. It's just a pity that we can't forbid reassignment altogether. -- nosy: +pitrou ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue17953] sys.modules cannot be reassigned
Brett Cannon added the comment: There is no good way to solve this. At the C level there interpreter struct has two key fields, sysdict and modules. The former is sys.__dict__ and the latter is sys.modules. But when you re-assign sys.modules you then break the assumption that sys.modules is the same dict as that contained in interp-modules. And this all goes out the window as the C code is expected to use interp-modules while the Python code in importlib only has access to sys.modules. The reason this used to work is your new dictionary was completely ignored and so we basically a no-op from the perspective of import (done in Python 2.7 but same result in any version up to Python 3.3):: import sys original_modules = sys.modules new_modules = sys.modules.copy() sys.modules = new_modules import pkg 'pkg' in original_modules True 'pkg' in new_modules False What really needs to happen is that sys.modules needs to be documented as something that cannot be replaced. If you really want to update it cleanly then do ``sys.modules.clear(); sys.modules.update(new_modules)``, but even that is tricky because removing certain modules will flat-out break Python. I have updated the issue to be a documentation one and added Python 3.4 to the affected versions. -- components: +Documentation -Interpreter Core keywords: +easy stage: - test needed type: behavior - versions: +Python 3.4 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue17953 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
