Django, mod_wsgi and virtual env

Question

I'm setting up Django with apache, mod_wsgi, virtual env

I have a virtual env that I want to use here: [Missleading name - long story!] /home/andy/Dev/python/async-mongo/

I downloaded mod_wsgi and compiled it with virtual_env as root

./configure --with-python=/home/andy/Dev/python/async-mongo/bin/python

I ran as root:

make install

I setup WSGIPythonHome & Path in http.conf

WSGIPythonHome /home/andy/dev/python/async-mongo/
WSGIPythonPath /home/andy/dev/python/async-mongo/lib/python2.6/site-packages
LoadModule wsgi_module /usr/lib/apache2/modules/mod_wsgi.so

I think I followed the instructions at http://code.google.com/p/modwsgi/wiki/VirtualEnvironments

When I run the 'Hello World' app it works

def application(environ, start_response):
    status = '200 OK'
    output = 'Hello World!'
    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)

    return [output]

When I try to import a module it fails:

import sys; raise Exception(sys.path)
def application(environ, start_response):
    status = '200 OK'
    output = 'Hello World!'
    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)
    print >> sys.stderr, 'sys.prefix = %s' % repr(sys.prefix)
    print >> sys.stderr, 'sys.path = %s' % repr(sys.path)
    return [output]

The error I see in the apache logs is:

[Fri Mar 30 15:09:53 2012] [notice] Apache/2.2.20 (Ubuntu) mod_wsgi/3.3 Python/2.6.7 configured -- resuming normal operations

........

Exception: ['/home/andy/dev/python/async-mongo', '/home/andy/dev/python/async-mongo/lib/python2.6/site-packages/setuptools-0.6c11-py2.6.egg', '/home/andy/dev/python/async-mongo/lib/python2.6/site-packages/pip-1.0.2-py2.6.egg', '/home/andy/dev/python/async-mongo/lib/python2.6/site-packages/txmongo-0.3-py2.6-linux-i686.egg', '/home/andy/dev/python/async-mongo/lib/python2.6', '/home/andy/dev/python/async-mongo/lib/python2.6/plat-linux2', '/home/andy/dev/python/async-mongo/lib/python2.6/lib-tk', '/home/andy/dev/python/async-mongo/lib/python2.6/lib-old', '/home/andy/dev/python/async-mongo/lib/python2.6/lib-dynload', '/usr/lib/python2.6', '/usr/lib/python2.6/plat-linux2', '/usr/lib/python2.6/lib-tk', '/home/andy/dev/python/async-mongo/lib/python2.6/site-packages']

I am guessing that somewhere somehow I am still referencing the old system level python but I can not understand where. How can I fix this?

Answer 1

You are raising an exception here:

import sys; raise Exception(sys.path)

Answer 2

The place to fiddle with sys.path is at your_application.wsgi. I don't think compiling mod_wsgi pointing to a virtualenv python binary is a good idea, the whole point of virtualenv is flexibility (having several versions of django playing nice in the same machine, for example).

My take on django, apache, wsgi and virtualenv is a my_application.wsgi file like this:

import os
import sys
import site

# Backup sys.path
prev_sys_path = list(sys.path)
# Add virtual environment to site directories:
site.addsitedir('/var/lib/python-environments/my_env/lib/python2.6/site-packages')

# settings.py sitting at /path/to/apps/my_application
os.environ['DJANGO_SETTINGS_MODULE'] = 'my_application.settings'
sys.path.append('/path/to/apps')

# start the trick
sys.path.extend([
   '/var/lib/python-environments/my_env/lib/python2.6/site-packages',
   '/var/lib/python-environments/my_env/lib/python2.6/site-packages/django/contrib/admindocs',
])
# Reorder syspath
new_sys_path = [p for p in sys.path if p not in prev_sys_path]
for item in new_sys_path:
    sys.path.remove(item)
# Make sure virtual env is first
sys.path[:0] = new_sys_path

import django.core.handlers.wsgi
application = django.core.handlers.wsgi.WSGIHandler()