Random switch from py2.7 to 3

[StephaneKazmierczak]

Hi,

While working on a notebook using python 2.7, from time to time the cell will switch to python 3 syntaxe.
for example trying to execute a cell, I will get error messages asking me to add () to my prints, I just have to close the notebook and reopen to fix the issues.

It is really strange as I didn't install python 3 kernel on the server that i am using and only have python 2 available from jupyter drop-down menu.

[takluyver]

Is it possible that you're running code containing from __future__ import print_function?

Can you check sys.version and sys.executable before and after it happens?

[StephaneKazmierczak]

Hi sorry for delay, I moved on to something else and forget to check here, but sys.version return

3.5.2 (default, Nov 17 2016, 17:05:23)
[GCC 5.4.0 20160609]

Also I am using the Linux layer on windows 10. The problem may come from that.

when starting python from command line:

$pyhton
Python 2.7.12 (default, Nov 19 2016, 06:48:10)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.

[StephaneKazmierczak]

I just fix it, the config for kernel/python2/kernel.json what using argv : [ "python"
I just replace by python by /usr/bin/python2.7 and now it is working, it is really strange as /usr/bin/python link to python2.7 but for some reason now it is working

[takluyver]

There's a special case in the code to interpret "python" as the same Python executable which is running the notebook server. So if your notebook server is running on Python 3, any kernel with "python" as the first argument will run with that too.

This has been causing some confusion. I have a plan to change how kernels are found more generally, which I hope will make it easier to understand as well: jupyter/jupyter_client#261