ImportWarning: sys.meta_path is empty

[foxx]

In some situations, if you run unittests after importing IPython, it will cause the following errors to be flooded in 3.4;

sys:1: ResourceWarning: unclosed file <_io.TextIOWrapper name='/dev/null' mode='w' encoding='UTF-8'>
/home/vagrant/.virtualenvs/vagrant/lib/python3.4/importlib/_bootstrap.py:2127: ImportWarning: sys.meta_path is empty
/home/vagrant/.virtualenvs/vagrant/lib/python3.4/importlib/_bootstrap.py:2127: ImportWarning: sys.meta_path is empty
/home/vagrant/.virtualenvs/vagrant/lib/python3.4/importlib/_bootstrap.py:2127: ImportWarning: sys.meta_path is empty
/home/vagrant/.virtualenvs/vagrant/lib/python3.4/importlib/_bootstrap.py:2127: ImportWarning: sys.meta_path is empty
... repeated hundreds of times ...

There is a fixed bug in Python and another repo with the same problem.

If I remove the following import line, the problem goes away;

from IPython import start_ipython

Clearly there is something not quite right with the way IPython has been packaged, importing a function from a package should not result in any runtime execution differences.

[minrk]

Can you provide a complete example that reproduces the issue? The only interaction IPython has with sys.meta_path is adding import hooks when deprecated modules are imported. It never removes items from sys.meta_path.

[jakirkham]

The sys.meta_path is an upstream issue in Python. It has been corrected in Python 3.5. I am not sure if a bugfix patch will be added for Python 3.4 or not. See more details here ( https://bugs.python.org/issue21049 ).

The ResourceWarning is caused by this line (

ipython/IPython/utils/io.py

Line 75 in a33a063

devnull = open(os.devnull, 'w')

) and can be fixed with this PR ( #8929 ).

[foxx]

Nice work, thanks guys!