python shell卡在退出处

Question

Python doesn't exit if I have imported two libraries in a certain order. I'm using the python libraries scitools and fenicstools .

In the python shell, the following will work:

import fenicstools
import scitools
exit()

This won't exit but hang (reversed the imports):

import scitools      # ok
import fenicstools   # ok
exit()               # gets me stuck, I can still exit with Ctrl+C

I can reproduce this on two Ubuntu 14.04 machines and am now at a complete loss. How do I even start debugging such an issue?

Background: I'm using sumatra to keep track of my numerical simulations. It gathers and logs the versions of the dependencies of my project. I thus have no control over the order in which it tries to do so. Result: It gets stuck.

Edit: Following @ErlVolton's suggestion, I tried pdb. Put the two imports in their problematic order in a file called test.py .

$ pdb test.py
> /home/gallomania/test.py(1)<module>()
-> import scitools
(Pdb) n
> /home/gallomania/test.py(2)<module>()
-> import fenicstools
(Pdb) n
--Return--
> /home/gallomania/test.py(2)<module>()->None
-> import fenicstools
(Pdb) exit

... This makes pdb not exit.

Answer 1

Use pdb to step through each operation and see which line of code fenicstools is hanging on in its __init__.py

https://docs.python.org/2/library/pdb.html

Example:

$ pdb test.py
> /home/cleekley/test/test.py(1)<module>()
-> import sys
(Pdb) s
> /home/cleekley/test/test.py(2)<module>()
-> import time
(Pdb) s
> /home/cleekley/test/test.py(4)<module>()
-> while True:
(Pdb) s
> /home/cleekley/test/test.py(5)<module>()
-> time.sleep(1)
(Pdb) s
> /home/cleekley/test/test.py(4)<module>()
-> while True:
(Pdb) quit