[Tutor] Need help with a virtual environment mess

Jim jf_byrnes at comcast.net
Mon May 7 14:04:23 EDT 2018

On 05/07/2018 12:02 PM, Mats Wichmann wrote:
> On 05/07/2018 10:16 AM, Jim wrote:
>> My understanding of VE's, based on some feedback from here, is you
>> install install the python you want on the system then use it to install
>> your VE. Then you install what ever you need to the VE. In my case I had
>> a working VE based on python 3.5 then I received an upgrade to the
>> python version 3.6 I had installed. After that I had problems with the
>> 3.5 VE that had been working.
> yes, this happens.
> the default behavior for virtualenv is to make links when creating the
> VE, which saves copying things but is vulnerable to breakage if the
> Python it's linking to receives major changes.  In the case of a
> distribution upgrading the Python version, a VE constructed against the
> old version will break if the links are version-specific.  Looking at
> one virtualenv I have, {VEPATH}/lib/python3.6 is full of such symlinks,
> e.g.:
> lrwxrwxrwx.  1 mats mats    26 Aug 17  2017 re.py ->
> /usr/lib64/python3.6/re.py
> Virtualenvs are cheap to recreate, so one approach is to just throw away
> the old one and make a new one.

My problem is right now the default python3 for my system is also 
affected. If I type python3 I will see python version 3.5.2 and I cannot 
import tkinter there either.

> you can also give virtualenv an option (--always-copy) to cause the
> created virtualenv to be more self-contained, at a cost of some space
> and tiem.
> There are plenty of tools for managing python versions and virtualenv.
> The python community changed directions a little bit recently, 'venv' is
> now the recommended approach:
> https://docs.python.org/3/library/venv.html

That is what I used to setup my VE's.

> pyenv can manage different Python versions if you're interested in that.

I am going to see if I can find some log file that would give me a clue 
about what happened during the update.

Regards,  Jim

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