/Virtualenv-Virtualenvwrapper-Usage

Inludes Description of How to Use Virtualenv and Virtualenvwrapper with Python

Virtualenv Virtualenvwrapper Usage

Inludes Description of How to Use Virtualenv and Virtualenvwrapper with Python

Installation

  • Using pip install virtualenv and virtualenvwrapper to the system.
$ sudo pip install virtualenv virtualenvwrapper
  • Create a .virtualenvs folder in your root
$ cd ~
$ mkdir .virtualenvs
  • Using vim add the following lines to your .bashrc
# virtualenv and virtualenvwrapper
export WORKON_HOME=$HOME/.virtualenvs
export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
source /usr/local/bin/virtualenvwrapper.sh
  • Restart the bash session. Alternativly run
source ~/.bashrc

Virtualenvwrapper Usage

  • Creating a virtualenv mkvirtualenv. It creates and start the env with [ENV_NAME]
$ mkvirtualenv [ENV_NAME] -p python[VERSION]
([ENV_NAME]) $
  • Deactivating an environment
([ENV_NAME]) $ deactivate
$
  • Activating an environment
$ workon [ENV_NAME]
([ENV_NAME]) $
  • Deleting an environment
$ rmvirtualenv [ENV_NAME]
  • Showing available virtualenvwrapper commands:
$ virtualenvwrapper
  add2virtualenv: add directory to the import path

  allvirtualenv: run a command in all virtualenvs

  cdproject: change directory to the active project

  cdsitepackages: change to the site-packages directory

  cdvirtualenv: change to the $VIRTUAL_ENV directory

  cpvirtualenv: duplicate the named virtualenv to make a new one

  lssitepackages: list contents of the site-packages directory

  lsvirtualenv: list virtualenvs

  mkproject: create a new project directory and its associated virtualenv

  mktmpenv: create a temporary virtualenv

  mkvirtualenv: Create a new virtualenv in $WORKON_HOME

  rmvirtualenv: Remove a virtualenv

  setvirtualenvproject: associate a project directory with a virtualenv

  showvirtualenv: show details of a single virtualenv

  toggleglobalsitepackages: turn access to global site-packages on/off

  virtualenvwrapper: show this help message

  wipeenv: remove all packages installed in the current virtualenv

  workon: list or change working virtualenvs

Environment Variable Management with Virtualenvwrapper

  • Virtualenv provides mechanism for environment variable management:
  • preactivate: This hook is run before this virtualenv is activated.
$ workon [ENV_NAME]
$ vim $VIRTUAL_ENV/bin/preactivate
#!/bin/bash
# This hook is run before this virtualenv is activated.

  • predeactivate: This hook is sourced before this virtualenv is deactivated.

  • postactivate: This hook is sourced after this virtualenv is activated.

  • postdeactivate: This hook is sourced after this virtualenv is deactivated.

  • Remember that if using this for environment variables that might already be set in your environment then the unset will result in them being completely unset on leaving the virtualenv. So if that is at all probable you could record the previous value somewhere temporary then read it back in on deactivate.
$ cat $VIRTUAL_ENV/bin/postactivate
#!/bin/bash
# This hook is run after this virtualenv is activated.
if [[ -n $SOME_VAR ]]
then
    export SOME_VAR_BACKUP=$SOME_VAR
fi
export SOME_VAR=apple

$ cat $VIRTUAL_ENV/bin/predeactivate
#!/bin/bash
# This hook is run before this virtualenv is deactivated.
if [[ -n $SOME_VAR_BACKUP ]]
then
    export SOME_VAR=$SOME_VAR_BACKUP
    unset SOME_VAR_BACKUP
else
    unset SOME_VAR
fi

TEST

$ echo $SOME_VAR
banana

$ workon myenv

$ echo $SOME_VAR
apple

$ deactivate

$ echo $SOME_VAR
banana

References

how-to-install-opencv-4-on-ubuntu

configuring-python-environment-with-virtualenvwrapper

setting-an-environment-variable-in-virtualenv