Installing python3 in a python2 virtual environment

Question

I have a Flask application that is running in a Python 2 virtual environment.

I'm looking to run a Python 3 program, so I need to install python3 into the virtual environment. How do I do this? Do I have to recreate the environment? Is this a difficult migration?

That doesn't sound feasible. You have to pick one python version for a virtual environment. — wim
– wim, Commented Dec 30, 2016 at 3:05

alex · Accepted Answer · 2018-05-31 19:22:26Z

16

It's not recommended to mix multiple versions of Python. In fact, I don't think it's even possible.

Creating a new virtualenv isn't difficult at all:

Get the list of modules in the current virtualenv

source /path/to/current/bin/activate
pip freeze > /tmp/requirements.txt

Create a new virtualenv. Either change into a suitable directory before executing the virtualenv command or give a full path.
```
deactivate
virtualenv -p python3 envname
```

Install modules

source envname/bin/activate
pip install -r /tmp/requirements.txt

That's it.

edited May 31, 2018 at 19:22

alex

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answered Dec 30, 2016 at 3:09

e4c5

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2 Comments

M Leonard Over a year ago

wow. yeah. it was that easy. one note... you're /tmp/requirements.txt spelling is inconsistent ;-) Question... How do I verify that that Flask App is using the venv? As long as I source it, is it automatically using it?

e4c5 Over a year ago

yes, if you source it it will be using the one in the virtualenv

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