"Nested" virtual environments

[Luca Cerone]

Dear all, is there a way to "nest" virtual environments?

I work on several different projects that involve Python programming.

For a lot of this projects I have to use the same packages (e.g. numpy, scipy, matplotlib and so on), while having to install packages that are specific
for each project.

For each of this project I created a virtual environment (using virtualenv --no-site-packages) and I had to reinstall the shared packages in each of them.

I was wondering if there is a way to nest a virtual environment into another,
so that I can create a "common" virtual environment  that contains all the
shared packages and then "specialize" the virtual environments installing the packages specific for each project.

In a way this is not conceptually different to using virtualenv --system-site-packages, just instead of getting access to the system packages a virtual environment should be able to access the packages of an other one.

Thanks a lot in advance for the help,
Luca