Python Virtual Environment – virtualenv

Chapter 174: Python Virtual Environment – virtualenv

A Virtual Environment (“virtualenv”) is a tool to create isolated Python environments. It keeps the dependencies required by different projects in separate places, by creating virtual Python env for them. It solves the “project A depends on version 2.xxx but, project B needs 2.xxx” dilemma, and keeps your global site-packages directory clean and manageable.

“virtualenv” creates a folder which contains all the necessary libs and bins to use the packages that a Python project would need.

Section 174.1: Installation

Install virtualenv via pip / (apt-get):
pip install virtualenv
OR
apt-get install python-virtualenv

Note: In case you are getting permission issues, use sudo.

Section 174.2: Usage

cd test_proj

Create virtual environment:

$ virtualenv test_proj
To begin using the virtual environment, it needs to be activated:
$ source test_project/bin/activate
To exit your virtualenv just type “deactivate”:
$ deactivate

Section 174.3: Install a package in your Virtualenv

If you look at the bin directory in your virtualenv, you’ll see easy_install which has been modified to put eggs and packages in the virtualenv’s site-packages directory. To install an app in your virtual environment:

source test_project/bin/activate
pip install flask

At this time, you don’t have to use sudo since the files will all be installed in the local virtualenv site-packages directory. This was created as your own user account.

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Section 174.4: Other useful virtualenv commands

lsvirtualenv : List all of the environments.

cdvirtualenv : Navigate into the directory of the currently activated virtual environment, so you can browse its site-packages, for example.

cdsitepackages : Like the above, but directly into site-packages directory.

lssitepackages : Shows contents of site-packages directory.

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