Python Adventures

Here I describe how I use virtualenvwrapper.

I keep my virtual environments in the default location (~/.virtualenvs folder). My Python projects are kept in Dropbox. If a project (call it “stuff” for instance) has a virtual env., then I add the suffix “_project” to the projects’s folder name (resulting “stuff_project” in this example). This way I can see it immediately (without entering the folder) that it has an attached venv.

In the stuff_project folder create a requirements.txt file that contains all the modules that you installed in your venv. This way you can re-create your venv on another machine and continue to work on yout project.

Let’s see a concrete example. Say I want to create a new Django project:

$ cd $HOME/Dropbox/python/webapps
$ mkdir stuff_project
# ^ every project file will be in this folder
$ cd stuff_project
$ django-admin.py startproject stuff
# ^ create the Django project
$ mkvirtualenv stuff_project
# ^ venv is created AND activated
$ pip install django
$ pip install django-extensions
# ^ useful extensions
$ pip freeze --local >requirements.txt
# ^ packages installed in the venv are listed in this file

Since I put the project folder in Dropbox, it will be synced on all my machines. What to do if I want to work on this project on another machine of mine (let’s call it “machine #2”)? The virtual environment will be missing. But there is no need to worry. We have a requirements.txt file and from this we can populate a newly created venv. Install virtualenvwrapper on machine #2 and create an empty venv for the project:

# actions to perform on machine #2:
$ cd $HOME/Dropbox/python/webapps/stuff_project
$ mkvirtualenv stuff_project
# ^ the venv is created and activated
$ pip install -r requirements.txt
# ^ packages are installed in the venv

When you are done with the project, deactivate the venv with the “deactivate” command. Since it’s too long, I put an alias on it:

alias off='deactivate'

If you install new packages in the venv, don’t forget to update the requirements.txt file ( pip freeze >requirements.txt )!