Issue
I have an existing virtualenv with a lot of packages but an old version of Django.
What I want to do is duplicate this environment so I have another environment with the exact same packages but a newer version of Django. How can I do this?
Solution
The easiest way is to use pip to generate a requirements file. A requirements file is basically a file that contains a list of all the python packages you want to install (or have already installed in case of file generated by pip), and what versions they're at.
To generate a requirements file, go into your original virtualenv, and run:
pip freeze > requirements.txt
This will generate the requirements.txt file for you. If you open that file up in your favorite text editor, you'll see something like:
Django==1.3
Fabric==1.0.1
etc...
Now, edit the line that says Django==x.x to say Django==1.3 (or whatever version you want to install in your new virtualenv).
Lastly, activate your new virtualenv, and run:
pip install -r requirements.txt
And pip will automatically download and install all the python modules listed in your requirements.txt file, at whatever versions you specified!
Answered By - rdegges