Installing Kivy on Raspberry Pi 3 and making it work with Python 3.4

Question

(This may be a duplicate of an unanswered question at How do I Install Kivy for python 3.4 on my raspberry? Is that possible? , but I'd like to add some details to this.)

I have followed the default instructions for Manual installation (On Raspbian Jessie) at https://kivy.org/docs/installation/installation-rpi.html , and Kivy runs ok with Python, only that the version of Python that Kivy works with is 2.7:

[INFO   ] [Kivy        ] v1.9.2.dev0, git-e831904, 20170422  
[INFO   ] [Python      ] v2.7.9 (default, Sep 17 2016, 20:26:04)

Trying to run the code with python3.4 code.py of course results in

Traceback (most recent call last):
  File "code.py", line 5, in <module>
    from kivy.app import App
ImportError: No module named 'kivy'

suggesting that Python 3.4 isn't set up with Kivy.

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I would be extremely grateful for pointers to how I could either

1. set up Kivy for Python 3.4 (as in other question), or
2. redirect library for Python 3.4 so as to have it work with the Kivy installed in the default (2.7) Python library somehow.

(2. may be possible with PYTHONPATH ... ? Which I don't see in the default .profile file, so I'm a bit confused...)

Answer 1

NOTE 1: this MAY BREAK other software dependent on Python2, so please beware.
EDIT 2 : step 4 onwards should alleviate the possible damage from the temporary switch.
NOTE 3: it may be necessary to install Kivy under Python2 first BEFORE step 1 for this to work properly.

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I think I've managed to find a solution for this:

1. Referring to this page, set default Python to 3.4 (per-user or system-wide, according to your needs):

   How to change from default to alternative Python version on Debian Linux https://linuxconfig.org/how-to-change-from-default-to-alternative-python-version-on-debian-linux

   At this point, python --version should give you Python 3.4.2.

2. Follow instructions on the regular Kivy Install Page:

   User’s Guide » Installation on Raspberry Pi
   https://kivy.org/docs/installation/installation-rpi.html

3. Test run a python script with Kivy use, using the python command, and see if the log shows the likes of

   [INFO   ] [Kivy        ] v1.9.2.dev0, git-388651a, 20170423  
   [INFO   ] [Python      ] v3.4.2 (default, Oct 19 2014, 13:31:11)
   

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If you have changed the system-wide default Python, then do the following as well, to minimize any damage to other applications:

4. Referring to the page in step 1, run

   # update-alternatives --config python

   and select the python2.7 path as your default python.

5. Check that python --version gives you Python 2.7.9 and that python3 --version gives you Python 3.4.2 at this point.

6. Test run the script in step 3, but using python3 instead, and check that it works as in step 3.