One of the main advantages of mod_python is the increase in performance over traditional CGI. Below are results of a very crude test. The test was done on a 1.2GHz Pentium machine running Red Hat Linux 7.3. Ab was used to poll 4 kinds of scripts, all of which imported the standard cgi module (because this is how a typical Python cgi script begins), then output a single word 'Hello!'. The results are based on 10000 requests with concurrency of 1:
Standard CGI: 23 requests/s Mod_python cgihandler: 385 requests/s Mod_python publisher: 476 requests/s Mod_python handler: 1203 requests/s
Apache processes requests in phases (i.e. read the request, parse headers, check access, etc.). Phases are implemented by functions called handlers. Traditionally, handlers are written in C and compiled into Apache modules. Mod_python provides a way to extend Apache functionality by writing Apache handlers in Python. For a detailed description of the Apache request processing process, see the Apache Developer Documentation, as well as the Mod_python - Integrating Python with Apache paper.
Currently only a subset of the Apache HTTP Server API is accessible via mod_python. It was never the goal of the project to provide a 100% coverage of the API. Rather, mod_python is focused on the most useful parts of the API and on providing the most “Pythonic” ways of using it.
Mod_python also provides a number features that fall in the category of web development, e.g. a parser for embedding Python in HTML (psp – Python Server Pager), a handler that maps URL space into modules and functions (Publisher Handler), support for session (Session – Session Management) and cookie (Cookie – HTTP State Management) handling.