Virtualenv and Virtualenvwrapper

virtualenv

• virtualenv is software for isolating python package environments (e.g. import paths).

• site-packages should mostly be for system-installed python and not python that you are installing as a user. [1]

• virtualenv ENV

• source ENV/bin/active

• Once the virtualenv is activated, the virtualenv’s python (and other executables) will be on your PATH and you will have a new environment variable, VIRTUAL_ENV, that points to the path of the virtualenv, as well as a deactivate function for deactivating the virtualenv [2].

• ENV/bin/deactive

• build with virtualenv --system-site-packages ENV, virtual environment will inherit packages from /usr/lib/python2.7/site-packages

• Environment variables and configuration files

  • Environment variable: VIRTUAL_<UPPER_NAME> eg: export VIRTUAL_PYTHON=/opt/python-3.3/bin/python
  • Config files: ~/.virtualenv/virtualenv.ini

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[virtualenv]
python=/opt/python-3.3/bin/python

• bootstrap example:

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import virtualenv
script = virtualenv.create_bootstrap_script('''
    def after_install(options, home_dir):
        print options, home_dir
''')
open('my_bootstrap.py', 'w').write(script)

virtualenvwrapper

• a set of extensions to virtualenv

• initialization steps:

  • export WORKON_HOME="$HOME/.virtualenvs"
  • source /usr/local/bin/virtualenvwrapper.sh

• mkvirtualenv foo

• cdvirtualenv

• workon list all virtualenv

• workon env1 switch between environements with workon

• deactive

• lssitepackages

• cdsitepackages

• setvirtualenvproject bind an existing virtualenv to an existing project

[1]: http://blog.ianbicking.org/site-packages-considered-harmful.html

[2]: https://developer.mozilla.org/en-US/docs/Python/Virtualenv