PyXMLi helps Python developers generate invoices in XMLi 2.0 (http://www.xmli.org), the open-source invoice format designed by Greendizer (http://greendizer.com).

Why another format?
Simply because none of the available formats was good enough for what its creators needed it for.

Design goals:
-    Human-readable, Web-friendly format; 
-    Carry data structures, not business logic;
-    Stand-alone, with every detail possible from creation to archiving;
-    Privilege existing standards whenever possible.

Features:
PyXMLi comes with a great deal of features to make it really easier for Python developers to:

-    Generate XMLi 2.0 invoices in their favorite language;
-    Strongly validate pretty much every field locally before sending their invoices; 
-    Sign their invoices using the XMLDsig standard and a simple RSA key.

Requirements:
-    Python 2.5+
-    lxml 2.3+
-    PyCrypto 2.6+

(Built-in setup will install all the dependencies automatically).

Compatibility:
PyXMLi is compatible with Google App Engine and their Python 2.7 runtime.

Edit app.yaml to add pyCrypto and lxml to the list of third-party modules you'd like to use. 

    libraries:
    - name: pycrypto
      version: 2.6
    
    - name: lxml
      version: 2.3

Setup:
Using pip:

    sudo pip install --upgrade pyxmli

Using easy_install:

    sudo easy_install --upgrade pyxmli
    
Using source code:

    sudo python setup.py install