Create a virtualenv from another virtualenv

Question

Can we create a virtualenv from an existing virtualenv in order to inherit the installed libraries?

In detail:

I first create a "reference" virtualenv, and add libraries (with versions fixed):

virtualenv ref
source ref/bin/activate
pip install -U pip==8.1.1     # <- I want to fix the version number
pip install -U wheel==0.29.0  # <- I want to fix the version number

Then:

virtualenv -p ref/bin/python myapp
source myapp/bin/activate
pip list

I get:

pip (1.4.1)
setuptools (0.9.8)
wsgiref (0.1.2)

How to get my installed libraries?

Similar question

I saw a similar question: Can a virtualenv inherit from another? .

But I want a isolated virtualenv which didn't use the referenced virtualenv, except for libraries installation. So, adding the specified directories to the Python path for the currently-active virtualenv, is not the solution.

Why doing that?

Well, we have an integration server which builds the applications (for releases and continuous integration) and we want to keep the control on libraries versions and make the build faster.

Create a relocatable virtualenv

I think I could use a relocatable virtualenv , that way:

1. create the ref virtualenv
2. make it relocatable: ``virtualenv --relocatable ref```

For "myapp":

• copy ref to myapp

What do you think of this solution? Is it reliable for a distribuable release?

Answer 1

You can solve your problem by using .pth files . Basically you do this:

virtualenv -p ref/bin/python myapp
realpath ref/lib/python3.6/site-packages > myapp/lib/python3.6/site-packages/base_venv.pth

After doing this and activating myapp , if you run pip list you should see all the packages from ref as well. Note that any packages installed in myapp would hide the respective package from ref .

Answer 2

当你安装第二个virtualenv时，你必须添加--system-site-packages标志。

virtualenv -p ref/bin/python myapp --system-site-packages

Answer 3

You may freeze list of packages from one env:

(ref) user@host:~/dir$ pip freeze > ref-packages.txt

Then install them:

(use) user@host:~/dir$ pip install -r ref-packages.txt

Answer 4

The pip version 1.4.1 was bundle with an old version of virtualenv . For example the one shipped with Ubuntu 14.04. You should remove that from your system and install the most recent version of virtualenv .

pip install virtualenv

This might require root permissions ( sudo ).

Then upgrade pip inside the virtual env pip install -U pip or recrete the env.

Answer 5

I think your problem can be solved differently. With use of PYTHONPATH . First we create ref virtaulenv and install all needed packages here

$ virtualenv ref
$ source ref/bin/activate
$ pip install pep8
$ pip list
> pep8 (1.7.0)
> pip (8.1.2)
> setuptools (26.1.1)
> wheel (0.29.0)

Then we create second virtaulenv use .

$ virtualenv use
$ source use/bin/activate
$ pip list
> pip (8.1.2)
> setuptools (26.1.1)
> wheel (0.29.0)

And now we can set our PYTHONPATH in this env to include ref's directories

$ export PYTHONPATH=PYTHONPATH:/home/path_to/ref/lib/python2.7/site-packages:/home/path_to/ref/local/lib/python2.7/site-packages
$ pip list
> pep8 (1.7.0)
> pip (8.1.2)
> setuptools (26.1.1)
> wheel (0.29.0)

As you see this way you just reference installed packages in ref's environment. Also note that we add this folders at the end so they will have lower priority.

NOTE : this are not all folders that exists in PYTHONPATH . I included this 2 because they are main ones. But if you will have some problems you can add other ones too, just lookup needed paths with this method how to print contents of PYTHONPATH