Can existing virtualenv be upgraded gracefully?

Question

I have a virtualenv created for Python 2.5 and want to "upgrade" it to Python 2.6.

Here is how it was originally set up:

virtualenv --no-site-packages -p python2.5 myenv 

I now run virtualenv in the same directory to upgrade:

virtualenv --no-site-packages -p python2.6 myenv ... Not overwriting existing python script myenv/bin/python (you must use myenv/bin/python2.6) ... Overwriting myenv/bin/activate with new content 

The default python is still 2.5, even though I can also specify 2.6. Is there any way to remove 2.5 entirely and have 'bin/python' point to 2.6 instead?

Answer 1

You can use the Python 2.6 virtualenv to "revirtual" the existing directory. You will have to reinstall all the modules you installed though. I often have a virtual directory for developing a module, and virtualenv the same directory with many versions of Python, and it works just fine. :)

Answer 2

In Python 3.3+ venv supports --upgrade flag

  --upgrade             Upgrade the environment directory to use this version                         of Python, assuming Python has been upgraded in-place. 

Usage:

python -m venv --upgrade YOUR_VENV_DIRECTORY 

I just upgraded my venv from Python 3.7.x to 3.8 on several projects without any issue.