Python Virtual Environments Cheat Sheet

Virtual environments make using Python a bit more manageable, especially when it comes to deploying Python programs and creating the requirements (able to use pip freeze > requirements.txt and only use packages necessary to that individual project). However, I commonly find myself forgetting some of the more basic commands. For Python 2 use pip, for Python 3 use pip3.

Downloading virtualenv

1. Download virtualenv using pip pip install virtualenv
2. Download virtualenvwrapper using pip pip install virtualenvwrapper. Virtual environment wrapper will make using virtual environments a little easier.
3. On a Mac:
   • Create a directory to store your virtual environments, i.e mkdir ~/Documents/Development/virtualenvs
   • vi ~/.bash_profile
   • Add to file:

     	export WORKON_HOME=~/Documents/Development/virtualenvs
     	source /usr/local/bin/virtualenvwrapper.sh

     view raw .bash_profile hosted with ❤ by GitHub
   • Save and quit (esc + :wq)
   • source ~/.bash_profile
   • Quit and reopen terminal to reload bash profile

Basic commands to use virtual environments

• lsvirtualenv: List your virtual environments
• mkvirtualenv [name]: Create a new virtual environment. Use the flag -ppython3.5 after name to create a Python 3.5 virtual environment.
• rmvirtualenv [name]: Remove a virtual environment
• workon [name]: Enter a virtual environment
• deactivate: Stop working on a virtual environment
• pip freeze > requirements.txt: View modules installed in current environment
• pip install -r requirements.txt: Install all modules in requirements.txt

Setting up virtual environments

• To make workon [name] go directly to the directory of the project directory, edit the /virtualenvs/postactivate and add:

  	#!/bin/bash
  	# This hook is sourced after every virtualenv is activated.
  	PS1="$_OLD_VIRTUAL_PS1"
  	PROJECT_DIR="$HOME/Documents/Development/virtualenvs/$(basename $VIRTUAL_ENV)"
  	if [ -d $PROJECT_DIR ]; then
  	# If we aren't already within the project dir, cd into it
  	if [[ ! `pwd` == "$PROJECT_DIR*" ]]; then
  	export PRE_VENV_ACTIVATE_DIR=`pwd`
  	cd "$PROJECT_DIR"
  	fi
  	fi
  	unset PROJECT_DIR

  view raw postactivate.bash hosted with ❤ by GitHub
• To make deactivate exit the project directory, edit the /virtualenvs/postdeactivate and add:

  	#!/bin/bash
  	# This hook is sourced after every virtualenv is deactivated.
  	if [ $PRE_VENV_ACTIVATE_DIR ]; then
  	cd $PRE_VENV_ACTIVATE_DIR
  	unset PRE_VENV_ACTIVATE_DIR
  	fi

  view raw postdeactivate.bash hosted with ❤ by GitHub
  • by Harry Marr