Skip to content

virtualenvs.md

Latest commit

 

History

History
160 lines (116 loc) · 3.04 KB

virtualenvs.md

File metadata and controls

160 lines (116 loc) · 3.04 KB
title Virtual environments
author Pierce Edmiston
theme metropolis

What's a virtual environment (venv)?

$ which python
/usr/local/bin/python

$ source ~/.venvs/madpy/bin/activate

(madpy) $ which python
/Users/pierce/.venvs/madpy/bin/python

(madpy) $ which pip
/Users/work/.venvs/madpy/bin/pip

Why use virtual environments (venvs)?

Different projects have different dependencies.

Project A needs pandas==0.18.0.
Project B needs pandas==0.16.0.

Deciding where to put them

  1. Put all venvs in a common folder.
~/.venvs/project-a/
~/.venvs/project-b/
  1. Put venvs in the project root.
project-a/venv/
project-b/venv/

Creating virtual environments

  1. Use venv module in the standard library.
$ python3 -m venv ~/.venvs/project-a
$ source ~/.venvs/project-a/bin/activate
(project-a) $
  1. For python2, use virtualenv.
$ pip install virtualenv  # third party
$ virtualenv ~/.venvs/project-a
$ source ~/.venvs/project-a/bin/activate
(project-a) $

Demo

Installing google_survey in a virtualenv.

# Create and activate new python3 virtualenv named madpy2
$ python3 -m venv ~/.venvs/madpy2
$ source ~/.venvs/madpy2/bin/activate

# Install google_survey from github
(madpy2) $ pip install \
git+git://github.com/madison-python/google-survey.git#egg=google_survey

# Test out google_survey
(madpy2) $ python -m google_survey madpy-habits-survey.yaml \
           > results.csv

# Deactivate
(madpy2) $ deactivate
$

virtualenvwrapper

virtualenvwrapper is a wrapper around venv creation.

$ mkvirtualenv project-a
$ workon project-a
(project-a) $

Install virtualenvwrapper with pip

$ pip install virtualenvwrapper  # !!! bootstrapping problem !!!

Configuration for virtualenvwrapper

# contents of ~/.bash_profile
# ...
export WORKON_HOME=$HOME/.venvs
source /usr/local/bin/virtualenvwrapper.sh

virtualenvwrapper saves you keystrokes

So you want to work on a new project, and you've got a text file of requirements to install.

$ python3 -m venv ~/.venvs/project-a
$ source ~/.venvs/project-a/bin/activate
(project-a) $ pip install -r requirements.txt
(project-a) $
$ mkvirtualenv project-a -r requirements.txt
(project-a) $

Other features of virtualenvwrapper

virtualenvwrapper               # list of commands
ls $VIRTUALENVWRAPPER_HOOK_DIR  # list of hooks

Installation and python2/python3 headaches

$ pip2 install virtualenvwrapper
$ mkvirtualenv project-a                   # python2
$ mkvirtualenv --python=python3 project-a  # python3

$ pip3 install virtualenvwrapper
$ mkvirtualenv project-a                   # python3
$ mkvirtualenv --python=python2 project-a  # python2

virtualenvwrapper overview

  1. pip3 install virtualenvwrapper
  2. vim ~/.bash_profile ← export WORKON_HOME and source virtualenvwrapper.sh
  3. source ~/.bash_profile
  4. mkvirtualenv project-a
  5. workon project-a

Other approaches to environment management

  • pyenv
  • Canopy by Enthought
  • Anaconda by Continuum