Come creare multipli ambienti Django con virtualenv

Often we must work on various "Django":http://www.djangoproject.com/ applications, each one dependent on different set of libraries. For examples, we are working on a Django 1.1 project and and we need to start a new one with the latest version of the framework. The best solution is to keep the various environments separate, in order to ensure that each project accesses only the libraries which it depends. Python offers us "virtualenv":http://pypi.python.org/pypi/virtualenv, a tool to create multiple isolated environments. Each environment is completely independent from the others and from the installed packages in system's site-packages folder. Let's then see how to create a virtualenv and install the latest version of Django (today 1.2.1). h1. 1- Install python-setuptools The first thing to do is to install python-setuptools in order to have access to the command "easy_install":http://pypi.python.org/pypi/setuptools and to easly download packages. Alternatively, you can get the same results using the package "pip":http://pypi.python.org/pypi/pip. Let us open a console and type the following commands: stefano@stefano-laptop:~$ sudo apt-get install python-setuptools Reading package lists... Done Building dependency tree Reading state information... Done python-setuptools is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 132 not upgraded. stefano@stefano-laptop:~$
 h1. 2- Install virtualenv The second step is to install the package virtualenv using easy_install:  stefano@stefano-laptop:~$ sudo easy_install virtualenv [sudo] password for stefano: Searching for virtualenv Reading http://pypi.python.org/simple/virtualenv/ Reading http://virtualenv.openplans.org Best match: virtualenv 1.4.9 Downloading http://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.4.9.tar.gz#md5=c49067cab242b5ff8c7b681a5a99533a Processing virtualenv-1.4.9.tar.gz Running virtualenv-1.4.9/setup.py -q bdist_egg --dist-dir /tmp/easy_install-3D0IWT/virtualenv-1.4.9/egg-dist-tmp-xe4LRm warning: no previously-included files matching '*.*' found under directory 'docs/_templates' Adding virtualenv 1.4.9 to easy-install.pth file Installing virtualenv script to /usr/local/bin Installed /usr/local/lib/python2.6/dist-packages/virtualenv-1.4.9-py2.6.egg Processing dependencies for virtualenv Finished processing dependencies for virtualenv 
 h1. 3- Create the virtual environment Once installed the package virtualenv we will need to create a space to host multiple environments. In my case, I've chose to create a directory in my home rather than in another writable folder in the filesystem.  stefano@stefano-laptop:~$ cd Progetti/Python/ stefano@stefano-laptop:~/Progetti/Python$ stefano@stefano-laptop:~/Progetti/Python$ mkdir virtualenvs stefano@stefano-laptop:~/Progetti/Python$ cd virtualenvs/ stefano@stefano-laptop:~/Progetti/Python/virtualenvs$ 
 Now we create the real virtualenv, called "Django-1.2-env. Note the argument added to the command virtualenv, --no-site-packages: so our virtual environment will have only a minimal set of libraries in his site-packages folder. We also note that all next commands will not need access as super user via sudo.  stefano@stefano-laptop:~/Progetti/Python/virtualenvs$ virtualenv --no-site-packages django-1.2-env New python executable in django-1.2-env/bin/python Installing setuptools............done. 
 h1. 4- Download Django in /tmp Open a new console and download the tarball with the latest version of the framework Django. For simplicity, I've downloaded the package to /tmp.  stefano@stefano-laptop:~$ cd /tmp/ stefano@stefano-laptop:/tmp$ wget http://www.djangoproject.com/download/1.2.1/tarball/ --2010-08-28 11:20:58-- http://www.djangoproject.com/download/1.2.1/tarball/ Resolving www.djangoproject.com... 64.207.133.18 Connecting to www.djangoproject.com|64.207.133.18|:80... connected. HTTP request sent, awaiting response... 301 Moved Permanently Location: http://media.djangoproject.com/releases/1.2/Django-1.2.1.tar.gz [following] --2010-08-28 11:20:59-- http://media.djangoproject.com/releases/1.2/Django-1.2.1.tar.gz Resolving media.djangoproject.com... 64.207.133.30 Connecting to media.djangoproject.com|64.207.133.30|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 6248006 (6.0M) [application/octet-stream] Saving to: `Django-1.2.1.tar.gz' 100%[======================================>] 6,248,006 590K/s in 12s 2010-08-28 11:21:11 (523 KB/s) - `Django-1.2.1.tar.gz' saved [6248006/6248006] 
 h1. 5- Installing Django in virtualenv At this point, unpack Django and activate the virtualenv (via the command "source virtualenvdir/bin/activate"). Once activated virtualenv, we'll find his name in the shell: (django-1.2-env)stefano@stefano-laptop  stefano@stefano-laptop:/tmp$ tar xzfv Django-1.2.1.tar.gz stefano@stefano-laptop:/tmp/Django-1.2.1$ source /home/stefano/Progetti/Python/virtualenvs/django-1.2-env/bin/activate (django-1.2-env)stefano@stefano-laptop:/tmp/Django-1.2.1$ (django-1.2-env)stefano@stefano-laptop:/tmp/Django-1.2.1$ python setup.py install 
 We verify here that Django is installed properly in the virtual site-packages:  stefano@stefano-laptop:~/Progetti/Python/virtualenvs/django-1.2-env$ ls lib/python2.6/site-packages/ django easy-install.pth setuptools-0.6c11-py2.6.egg Django-1.2.1-py2.6.egg-info pip-0.7.2-py2.6.egg setuptools.pth 
 h1. 6- Create a new project At this point, we can create a new project using the command django-admin.py as required by the framework.  (django-1.2-env)stefano@stefano-laptop:/tmp/Django-1.2.1$ cd /home/stefano/Progetti/Python/ (django-1.2-env)stefano@stefano-laptop:~/Progetti/Python$ (django-1.2-env)stefano@stefano-laptop:~/Progetti/Python$ django-admin.py startproject newdjangoapp (django-1.2-env)stefano@stefano-laptop:~/Progetti/Python$ cd newdjangoapp/ (django-1.2-env)stefano@stefano-laptop:~/Progetti/Python/newdjangoapp$ ls __init__.py manage.py settings.py urls.py 
 In conclusion, we can say that virtualenv is an excellent solution to create environments fully independent and designed to accommodate each individual project. In this way, we avoid conflicts of libraries and have the opportunity to try new configurations without creating problems for other applications.