How to use virtualenv to manage the dependencies of a Python application?

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How to use virtualenv to manage the dependencies of a Python application?

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#1 by (23 votes)

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I need to manage the dependencies of a Python application I'm developing, so it's easy for other team developers to be able to work on the project using the same versions of the packages I'm using.

Can I do this with virtualenv ? How?

python

asked by anonymous 11.12.2013 / 17:50

1 answer

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score 23 · Accepted Answer

virtualenv assembles a "virtual" Python environment, storing all dependencies in a directory.

Personally, I like using the virtualenvwrapper , which is a set of scripts that make the mechanics of creating these environments a bit easier.

The steps to set up a virtual environment in Ubuntu with virtualenvwrapper are:

Install virtualenvwrapper:

sudo pip install virtualenvwrapper

echo source /usr/local/bin/virtualenvwrapper.sh >> ~/.bashrc

Create a directory where your virtual environments will be:

mkdir ~/.virtualenvs

Set the virtualenvwrapper WORKON_HOME environment variable in ~/.bashrc :

echo 'export WORKON_HOME=$HOME/.virtualenvs' >> ~/.bashrc && . ~/.bashrc

The virtualenvwrapper configuration is ready. Create a new virtual environment with an easy-to-type name:

mkvirtualenv web

This command will create an environment with the web name and enable it, indicating the environment name at the shell prompt - it will look something like (web) [user @ host] $ . You can exit the environment at any time by using the deactivate command and restart it with the workon web command.

Inside the environment, you can install the required dependencies using pip , which will install just inside the environment, example for an application Flask :

pip install flask

After installation, you can create a file with list of dependencies using:

pip freeze -l > requirements.txt

This will generate a requirements.txt file with content similar to:

Flask==0.10.1
Jinja2==2.7.1
MarkupSafe==0.18
Werkzeug==0.9.4
itsdangerous==0.23

And that's it! Now when another developer wants to make sure that they are using the same dependencies as you, he can create a virtualenv as well, and install the dependencies from that same file, using the command:

pip install -r requirements.txt