How to use Python virtualenv

Question

The scenario is: I am on Ubuntu 11 which comes with Python 2.7, I want to run Mozilla JetPack which supports Python 2.5/2.6 and Google App Engine which only supports Python 2.5.

Read that its not a good idea to remove Python 2.7 as Ubuntu maybe using it. So the correct way is to use virtualenv. But I am quite lost using it. I installed Python 2.5 in /usr/local/python25 following this guide

I tried

jiewmeng@JM:/usr/local/python25/bin$ ./python --version
Python 2.5.5
jiewmeng@JM:/usr/local/python25/bin$ ./python virtualenv /works/tmp/test
./python: can't open file 'virtualenv': [Errno 2] No such file or directory

then the below works but I will be using Python 2.7

jiewmeng@JM:/usr/local/python25/bin$ virtualenv /works/tmp/test
New python executable in /works/tmp/test/bin/python
Installing distribute.................................................................................................................................................................................done.
jiewmeng@JM:/usr/local/python25/bin$ cd /works/tmp/test/bin
jiewmeng@JM:/works/tmp/test/bin$ ls
activate  activate_this.py  easy_install  easy_install-2.7  pip  python
jiewmeng@JM:/works/tmp/test/bin$ ./python --version
Python 2.7.1+

Also, how do I then run Mozilla JetPack or Google App Engine with this version of Python? Sorry I am new to Python (and Linux/Ubuntu)

Answer 1

Outline:

• First cd to /usr/local/python25/bin
• Download setuptools for Python2.5 (setuptools-0.6c11-py2.5.egg)
• Install it (sh setuptools-0.6c11-py2.5.egg).
• Now install pip (easy_install pip).
• Install virtualenv and virtualenvwrapper using pip (pip install v... etc.).
• Configure WORKON_HOME for virtualenv wrapper to work (export WORKON_HOME = $HOME/.virtualenvs). You can use any other directory you want (not just $HOME/.virtualenvs). Just make sure to use the full path.
• Now create a virtualenv (mkvirtualenv foobar).
• Switch to the new virtualenv (workon foobar).
• Now install GAE, JetPack and whatever you want using pip install blah

Why did your install not work?

Looks like you did not install virtualenv for Python2.5. Hence this will not work.

jiewmeng@JM:/usr/local/python25/bin$ ./python virtualenv /works/tmp/test

You can check by running ls command in that directory. I suspect you won't find virtualenv file there.

However this worked for you.

jiewmeng@JM:/usr/local/python25/bin$ virtualenv /works/tmp/test

Because it is using the virtualenv file for system default Python2.7. You can check which virtualenv and opening the virtualenv script. You'll see that the #! will point to system default python.

So you need to install the easy_install and pip for Python 2.5 before you can create virtualenv for Python 2.5. Just follow the steps outlined above.