[I was doing this in order to benefit from some of the django-command-extension functionalities]

1. Get graphviz here and install it (should be straightforward)

2. Download PyGraphViz. Make sure you download the source package. It’s possible to install it through easy_install but it would throw the following error:

bash-3.2$ easy_install pygraphviz
Searching for pygraphviz
Reading http://pypi.python.org/simple/pygraphviz/
Reading http://networkx.lanl.gov/pygraphviz
Reading http://networkx.lanl.gov/wiki/download
Reading http://sourceforge.net/project/showfiles.php?group_id=122233&package_id=161979
Reading http://networkx.lanl.gov/download
Best match: pygraphviz 0.99.1
Downloading http://pypi.python.org/packages/source/p/pygraphviz/pygraphviz-0........
Processing pygraphviz-0.99.1.zip
Running pygraphviz-0.99.1/setup.py -q bdist_egg --dist-dir /var/folders/Cm/C.........
Trying pkg-config
/bin/sh: pkg-config: command not found
/bin/sh: pkg-config: command not found
Trying dotneato-config
Failed to find dotneato-config

Your graphviz installation could not be found.

Either the graphviz package is missing on incomplete
(binary packages graphviz-dev or graphviz-devel missing?).

If you think your installation is correct you will need to manually
change the include_path and library_path variables in setup.py to
point to the correct locations of your graphviz installation.

The current setting of library_path and include_path is:
library_path=None
include_path=None

error: None

3. Change setup.py by specifying where your graphViz installation is [more info here]:

# library_path=None
library_path='/usr/local/lib/graphviz'
# include_path=None
include_path='/usr/local/include/graphviz'

4. Install:

bash-3.2$ python setup.py install
library_path=/usr/local/lib/graphviz
include_path=/usr/local/include/graphviz
running install
running build
running build_py
creating build/lib.macosx-10.4-i386-2.5
creating build/lib.macosx-10.4-i386-2.5/pygraphviz
copying pygraphviz/__init__.py -> build/lib.macosx-10.4-i386-2.5/pygraphviz
copying pygraphviz/agraph.py -> build/lib.macosx-10.4-i386-2.5/pygraphviz
[...... etc. etc.......]

5. Enjoy!:

>>> import pygraphviz as pgv
>>> G=pgv.AGraph()
>>> G.add_node('a')
>>> G.add_edge('b','c')
>>> G
strict graph {
        a;
        b -- c;
}

#To load a dot file use

>>> G=pgv.AGraph("file.dot")