Adding Python 2 kernel to Ipython

Question

I have Jupyter Notebook installed on Ubuntu. Python 2 and 3 run OK on the terminal but only Python 3 shows up on IPython. I am trying to get both kernels (2 and 3) up on IPython.

I've tried to manually install ipykernel from https://github.com/ipython/ipykernel which was successful but still can't get Python 2 kernel to show up. I also tried:

> sudo ipython2 kernelspec install-self

And got the error: ImportError: No module named shutil_get_terminal_size

Next, i tried:

python2 -m pip install --upgrade ipykernel 
python2 -m ipykernel install

The second line returned an error:

/usr/bin/python2: No module named shutil_get_terminal_size; 'ipykernel' is a package and cannot be directly executed

I guess the challenge is with the module named shutil_get_terminal_size. Please, kindly advise on how I can fix this. I read this post: https://github.com/ipython/ipython/issues/9416 but can't make much sense of it.

Thank you!

Not exactly an answer, but why not use separate virtual environments for Python 2 and Python 3? This is what I do. — seanmus
– seanmus, Commented Jun 8, 2016 at 21:52

Stephen Balousek · Accepted Answer · 2016-08-05 02:30:29Z

I experienced the same issue and found that a backports package was installed in both the Python 2.7 system site directory and the user site directory. Furthermore, the backports.shutil_get_terminal_size package was only in the system site directory:

$ ls -l $(find / -name 'backports' 2>/dev/null)
/root/.local/lib/python2.7/site-packages/backports:
total 0
drwxr-xr-x 1 root root 88 Aug  4 16:04 configparser

/usr/lib/python2.7/site-packages/backports:
total 8
-rw-r--r-- 1 root root  75 Aug  4 17:58 __init__.py
-rw-r--r-- 1 root root 267 Aug  4 17:58 __init__.pyc
drwxr-xr-x 1 root root 128 Aug  4 17:58 shutil_get_terminal_size

When Python executes an import statement, it looks in the user site directory first, and then looks in the system site directory. Since the shutil_get_terminal_size package is not in the backports package in the user site directory, that import will always fail. Here's what the import error looks like in its minimal form:

$ echo "from backports.shutil_get_terminal_size import get_terminal_size; \
        print(get_terminal_size())" | python2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named shutil_get_terminal_size

Adding the -s option on the python command line tells Python to not use the user site directory, and the import command succeeds:

$ echo "from backports.shutil_get_terminal_size import get_terminal_size; \
        print(get_terminal_size())" | python2 -s
terminal_size(columns=319, lines=104)

The install command also succeeds when the -s option is added to the python command line:

$ python2 -s -m ipykernel install
Installed kernelspec python2 in /usr/local/share/jupyter/kernels/python2

How the backports package got into the user site directory in the first place is still a mystery.

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