virtualenv is a tool to build sandbox(ed) or isolated Python environments. Using it you can create multiple isolated Python development environments each with their own isolated 'site-packages', which basically means giving yourself a playground which you might as well need during all the hacking. The page here http://pypi.python.org/pypi/virtualenv has a lot of details on how you can go about installing it and then creating your own sand boxes. Here is what you would do on a Ubuntu box, if you have setuptools installed:

Installation:

$sudo easy_install virtualenv

Searching for virtualenv
Reading http://pypi.python.org/simple/virtualenv/
Best match: virtualenv 1.3.2
Downloading http://pypi.python.org/packages/2.5/v/virtualenv/virtualenv-1.3.2-py2.5.egg#md5=f2cd2b10b8be8b57e74cb1830fc0b504
Processing virtualenv-1.3.2-py2.5.egg
creating /home/amit/virtualenv-local/lib/python2.5/site-packages/virtualenv-1.3.2-py2.5.egg
Extracting virtualenv-1.3.2-py2.5.egg to /home/amit/virtualenv-local/lib/python2.5/site-packages
Adding virtualenv 1.3.2 to easy-install.pth file
Installing virtualenv script to /home/amit/virtualenv-local/bin

Installed /home/amit/virtualenv-local/lib/python2.5/site-packages/virtualenv-1.3.2-py2.5.egg
Processing dependencies for virtualenv
Finished processing dependencies for virtualenv

Creating a isolated Python environment:

$ virtualenv --no-site-packages virtual-env-1
virtualenv --no-site-packages virtual-env-1
New python executable in virtual-env-1/bin/python
Installing setuptools............done.

The above command creates a new Python virtualenv with the name 'virtual-env-1' under your pwd. Couple of things to note:

• --no-site-packages: This option makes sure that when you are using the Python interpreter, it will *not* look into the global site-packages for third party packages (See this discussion for more on this topic)
• setuptools is installed automatically, so that you can start doing a easy_install (and more) in your Python environment just created

Okay, so your sandbox is ready. Let us see, what is in there:

.
|-- bin
|   |-- activate
|   |-- activate_this.py
|   |-- easy_install
|   |-- easy_install-2.5
|   `-- python
|-- include
|   `-- python2.5 -> /usr/include/python2.5
`-- lib
`-- python2.5
 |-- UserDict.py -> /usr/lib/python2.5/UserDict.py
 |-- UserDict.pyc -> /usr/lib/python2.5/UserDict.pyc
 |-- codecs.py -> /usr/lib/python2.5/codecs.py
 |-- codecs.pyc -> /usr/lib/python2.5/codecs.pyc
 |-- config -> /usr/lib/python2.5/config
 |-- copy_reg.py -> /usr/lib/python2.5/copy_reg.py
 |-- copy_reg.pyc -> /usr/lib/python2.5/copy_reg.pyc
 |-- distutils
 |   |-- __init__.py
 |   |-- __init__.pyc
 |   `-- distutils.cfg
 |-- encodings -> /usr/lib/python2.5/encodings
 |-- fnmatch.py -> /usr/lib/python2.5/fnmatch.py
 |-- fnmatch.pyc -> /usr/lib/python2.5/fnmatch.pyc
 |-- lib-dynload -> /usr/lib/python2.5/lib-dynload
 |-- locale.py -> /usr/lib/python2.5/locale.py
 |-- locale.pyc -> /usr/lib/python2.5/locale.pyc
 |-- no-global-site-packages.txt
 |-- ntpath.py -> /usr/lib/python2.5/ntpath.py
 |-- ntpath.pyc -> /usr/lib/python2.5/ntpath.pyc
 |-- orig-prefix.txt
 |-- os.py -> /usr/lib/python2.5/os.py
 |-- os.pyc -> /usr/lib/python2.5/os.pyc
 |-- posixpath.py -> /usr/lib/python2.5/posixpath.py
 |-- posixpath.pyc -> /usr/lib/python2.5/posixpath.pyc
 |-- re.py -> /usr/lib/python2.5/re.py
 |-- re.pyc -> /usr/lib/python2.5/re.pyc
 |-- site-packages
 |   |-- easy-install.pth
 |   |-- setuptools-0.6c9-py2.5.egg
 |   `-- setuptools.pth
 |-- site.py
 |-- site.pyc
 |-- sre.py -> /usr/lib/python2.5/sre.py
 |-- sre.pyc -> /usr/lib/python2.5/sre.pyc
 |-- sre_compile.py -> /usr/lib/python2.5/sre_compile.py
 |-- sre_compile.pyc -> /usr/lib/python2.5/sre_compile.pyc
 |-- sre_constants.py -> /usr/lib/python2.5/sre_constants.py
 |-- sre_constants.pyc -> /usr/lib/python2.5/sre_constants.pyc
 |-- sre_parse.py -> /usr/lib/python2.5/sre_parse.py
 |-- sre_parse.pyc -> /usr/lib/python2.5/sre_parse.pyc
 |-- stat.py -> /usr/lib/python2.5/stat.py
 |-- stat.pyc -> /usr/lib/python2.5/stat.pyc
 |-- types.py -> /usr/lib/python2.5/types.py
 `-- types.pyc -> /usr/lib/python2.5/types.pyc

10 directories, 45 files

The directory tree is pretty straight forward and spend some time looking at it. Now you can do two things:

• Make this the default Python interpreter, using 'activate_this.py'
• or, simply refer to it using the full pathname, such as : ~/virtual-env-1/bin/python

Using 'virtualenv' on NetBeans IDE for Python:

Coming to the main focus of this post, you can use your newly created virtualenv with the NetBeans IDE for Python. Just add a new platform using Tools > Python Platforms > New: 

                               

Once added, you can verify the Python Path: 

Now, you can either make it the default platform or make your use of this platform for your selected experimental projects!

Your Python test bed is ready!