= Converting Django models into Graphviz DOT files =

Inspired by [http://www.hackdiary.com/archives/000093.html this nice hack by Matt Biddulph] I set out to create a similar thing for Django models. Below is an initial implementation, and here are some results generated with the OS X version of Graphviz:

 * Graphviz DOT files for the Zyons project: [http://cavedoni.com/2006/08/zyons-comment.dot comment] [http://cavedoni.com/2006/08/zyons-event.dot event] [http://cavedoni.com/2006/08/zyons-forum.dot forum] [http://cavedoni.com/2006/08/zyons-openid.dot openid] [http://cavedoni.com/2006/08/zyons-prefs.dot prefs] [http://cavedoni.com/2006/08/zyons-sessions.dot sessions] [http://cavedoni.com/2006/08/zyons-tag.dot tag]
 * Resulting graphs in PDF: [http://cavedoni.com/2006/08/zyons-comment.pdf comment] [http://cavedoni.com/2006/08/zyons-event.pdf event] [http://cavedoni.com/2006/08/zyons-forum.pdf forum] [http://cavedoni.com/2006/08/zyons-openid.pdf openid] [http://cavedoni.com/2006/08/zyons-prefs.pdf prefs] [http://cavedoni.com/2006/08/zyons-sessions.pdf sessions] [http://cavedoni.com/2006/08/zyons-tag.pdf tag]

 * Other samples:
   * [http://cavedoni.com/2006/08/camera-001.dot generated dot file]: resulting image in [http://cavedoni.com/2006/08/camera-001.pdf PDF], 
{{{
#!html
<a href="http://code.djangoproject.com/attachment/wiki/DjangoGraphviz/camera-001.png">PNG</a>
}}}
   * [http://cavedoni.com/2006/08/mincer-001.dot generated dot file]: resulting image in [http://cavedoni.com/2006/08/mincer-001.pdf PDF], 
{{{
#!html
<a href="http://code.djangoproject.com/attachment/wiki/DjangoGraphviz/mincer-001.png">PNG</a>
}}}

You might also be interested in [http://www.exit66.com/diagram.zip this Django app by Andrew Barilla ] from which I borrowed some ideas, that displays the graphviz results directly from the web.

{{{
#!python
#!/usr/bin/python
"""Django model to DOT (Graphviz) converter
by Antonio Cavedoni <antonio@cavedoni.org>

Make sure your DJANGO_SETTINGS_MODULE is set to your project and call 
the script like this:

  $ python modelviz.py <app_label> > <filename>.dot

Changelog

0.4
Fixed OneToOneField support (thanks, limodou)

0.3
Added support for GenericRelation and OneToOneField

0.2
Changed display (shape="record", thanks Malcolm Tredinnick), 
fixed arrow direction, added display of model attributes 
(thanks, Russell Keith-Magee)

0.1
First release.
"""

__version__ = "0.4"
__license__ = "Python"
__author__ = "Antonio Cavedoni <http://cavedoni.com/"
__contributors__ = [
   "Stefano J. Attardi <http://attardi.org/>",
   "limodou <http://www.donews.net/limodou/>"
   ]

from django.db import models
from django.db.models import get_models
from django.db.models.fields.related import \
    ForeignKey, OneToOneField, ManyToManyField
from django.db.models.fields.generic import GenericRelation

def generate_dot(app_label):
   app = models.get_app(app_label)

   print "digraph %s {" % ('"' + app.__name__ + '"')
   print """  fontname = "Helvetica"
  fontsize = 8
      
  node [
    fontname = "Helvetica"
    fontsize = 8
    shape = "record"
  ]
   edge [
    fontname = "Helvetica"
    fontsize = 8
  ]
"""
   for o in get_models(app):
      nodes = []
      nodes.append("""  %s [
    label = "{%s |""" % (o.__name__, o.__name__))

      # model attributes
      for field in o._meta.fields:
         nodes.append('%s : %s\\l' % (field.name, type(field).__name__))
         
      if o._meta.many_to_many:
         for field in o._meta.many_to_many:
            nodes.append('%s : %s\\l' % (field.name, type(field).__name__))

      nodes.append(""" }"\n]\n""")
      print "".join(nodes)

      # relations
      rel = []

      for field in o._meta.fields:
         if isinstance(field, ForeignKey):
            _rel = ' %s -> %s [label="%s"];' % \
                (o.__name__, field.rel.to.__name__, type(field).__name__)
            if _rel not in rel:
               rel.append(_rel)
         elif isinstance(field, OneToOneField):
               _rel = '  %s -> %s [label="%s"] [arrowhead=none arrowtail=none];' % (o.__name__, field.rel.to.__name__, type(field).__name__)
               if _rel not in rel:
                  rel.append(_rel)

      for field in o._meta.fields:
         if isinstance(field, ForeignKey):
            _rel = ' %s -> %s [label="%s"];' % \
                (o.__name__, field.rel.to.__name__, type(field).__name__)
            if _rel not in rel:
               rel.append(_rel)

      if o._meta.many_to_many:
         for field in o._meta.many_to_many:
            if isinstance(field, ManyToManyField):
               _rel = '  %s -> %s [label="%s"] [arrowhead=normal arrowtail=normal];' % \
                   (o.__name__, field.rel.to.__name__, type(field).__name__)
               if _rel not in rel:
                  rel.append(_rel)

            if isinstance(field, GenericRelation):
               _rel = '  %s -> %s [label="%s"] [style="dotted"] [arrowhead=normal arrowtail=normal];' % \
                   (o.__name__, field.rel.to.__name__, type(field).__name__)
               if _rel not in rel:
                  rel.append(_rel)

      print "\n".join(rel)

   print "}"

if __name__ == "__main__":
   import sys
   app_label = sys.argv[1]
   generate_dot(app_label)
}}}