Issue 1562822: importing threading in a thread does not work (original) (raw)
Created on 2006-09-21 11:59 by steevel, last changed 2022-04-11 14:56 by admin. This issue is now closed.
Messages (6)
Author: Jaster (steevel)
Date: 2006-09-21 11:59
I got across this while trying to use MySQLdb in a thread. Since MySQLdb imports decimal I got the same error there.
Code: (This happens in both 2.4 and 2.5)
import thread, time, sys if len(sys.argv) > 1: import threading
def test (): import decimal print 'Exiting test.'
thread.start_new_thread(test, ()) time.sleep(1)
Output: $ ./thread.py 1 Exiting test.
$ ./thread.py Exiting test. Error in atexit._run_exitfuncs: Traceback (most recent call last): File "/usr/local/python2.5/lib/python2.5/atexit.py", line 24, in _run_exitfuncs func(*targs, **kargs) File "/usr/local/python2.5/lib/python2.5/threading.py", line 656, in __exitfunc self._Thread__delete() File "/usr/local/python2.5/lib/python2.5/threading.py", line 540, in __delete del _active[_get_ident()] KeyError: -1209698640 Error in sys.exitfunc: Traceback (most recent call last): File "/usr/local/python2.5/lib/python2.5/atexit.py", line 24, in _run_exitfuncs func(*targs, **kargs) File "/usr/local/python2.5/lib/python2.5/threading.py", line 656, in __exitfunc self._Thread__delete() File "/usr/local/python2.5/lib/python2.5/threading.py", line 540, in __delete del _active[_get_ident()] KeyError: -1209698640
Author: Josiah Carlson (josiahcarlson) * 
Date: 2006-09-22 03:48
Logged In: YES user_id=341410
I believe it is an issue with the import lock.
If you 'import decimal' prior to starting up your subthread, everything will run fine.
Author: Jaster (steevel)
Date: 2006-09-22 17:56
Logged In: YES user_id=1117967
I don't get this interface. Why can't I post a comment? To josiahcarlson: The program I'm currently writing is module based and I don't know what python modules my users will import. It shouldn't matter tho, either this is a "bug" or it needs to go in the documentation that you can't import them in a thread if you havent already imported them before.
Author: Josiah Carlson (josiahcarlson) *
Date: 2006-09-22 20:25
Logged In: YES user_id=341410
It's not so much that you can't import in a thread, it's that you can't import in a thread when the importer is running in another thread.
When you run a module via 'python module.py', Python compiles that module into bytecode, then imports the module, which results in the module being executed. The execution of the module performs the various imports, function definitions, class definitions, etc. When you start up a thread while the module is being imported, the import lock doesn't know what to do and bails out, leaving you with the situation you are having.
Try rewriting your module like: import thread import time import decimal
def test(): import decimal print "exiting test"
def main(): thread.start_new_thread(test, ()) time.sleep(1)
Then running it via: python -c "import tmodule;tmodule.main()"
And really, aside from "importing in a thread can be troublesome, if you don't know what you are doing, don't do it", what kind of documentation change would you suggest, and where would it go?
Author: Daniel Diniz (ajaksu2) *
Date: 2009-02-12 00:58
Here's the output of trunk (debug) for OP's test:
./python ../thread.py Exiting test. Exception KeyError: KeyError(-1210869568,) in <module 'threading' from '~/trunk-py/Lib/threading.pyc'> ignored [31071 refs]
Author: Brett Cannon (brett.cannon) * 
Date: 2009-03-30 23:21
So the failure stems from threading being imported by decimal in a thread itself. This is just not going to be supported as it confuses threading as to what thread was the main thread.
Closing as "won't fix".
History
Date
User
Action
Args
2022-04-11 14:56:20
admin
set
github: 44003
2009-03-30 23:21:11
brett.cannon
set
status: open -> closed
resolution: wont fix
messages: +
title: decimal module borks thread -> importing threading in a thread does not work
2009-02-12 00:58:31
ajaksu2
set
nosy: + ajaksu2
type: behavior
messages: +
2009-02-11 03:12:23
ajaksu2
set
assignee: brett.cannon
nosy: + brett.cannon
2006-09-21 11:59:41
steevel
create