[ python-Bugs-1175194 ] import statement likely to crash if module launches threads

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Bugs item #1175194, was opened at 2005-04-01 21:11
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Category: Threads
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Jeff Stearns (jeffstearns)
Assigned to: Nobody/Anonymous (nobody)
Summary: import statement likely to crash if module launches threads

Initial Comment:
I have a simple module which launches multiple HTTP client threads.

The main thread creates 10 HTTP clients, each of which fetches 
documents from a web server.  The main thread then simply goes to 
sleep while the client threads work. The threads are launched when 
the module is imported.

If I launch the script via
  python bug1.py
it launches and runs OK, and dies cleanly upon ^C.

But if I launch the script via
  python -c 'import bug1'
it hangs at launch, and dumps core upon ^C.

Here's an example:

jps at cure> ./python -c 'import bug1'
Using 10 threads
cccccccccc  <- [program hangs here]
Traceback (most recent call last):
  File "<string>", line 1, in ?
  File "test/bug1.py", line 55, in ?
    run (10)
  File "test/bug1.py", line 50, in run
    time.sleep (30000)
KeyboardInterrupt
Fatal Python error: PyImport_GetModuleDict: no module dictionary!
Aborted (core dumped)

You might argue that it's inappropriate to launch threads from within  
import statement, but I can't find a specific prohibition against it.

In any event, it shouldn't cause the interpreter to crash.

Please note that the crash isn't consistent. Sometimes the import 
statement doesn't lead to a crash.

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