Pesto is a library for Python web applications. Its aim is to make writing WSGI web applications easy and fun. Pesto isn’t a framework – how you integrate with databases, what templating system you use or how you prefer to organize your source files is up to you. Above all, Pesto aims to be small, well documented and well tested.

Pesto makes it easy to:

  • Map any URI to any part of your application.
  • Produce unicode aware, standards compliant WSGI applications.
  • Interrogate WSGI request information – form variables and HTTP request headers.
  • Create and manipulate HTTP headers, redirects, cookies etc.
  • Integrate with any other WSGI application or middleware, giving you access to a vast and growing resource.


Indices and tables


A very basic web application to demonstrate handling a request and creating a response:

from pesto import to_wsgi, Response

def handler(request):
    return Response([
        "<body><h1>Whoa Nelly!</h1></body>",

if __name__ == "__main__":
    from wsgiref import simple_server
    httpd = simple_server.make_server('', 8080, to_wsgi(handler))

Pesto handler functions typically take a Request object as an argument and should return a Response object.

A longer example using the DispatcherApp class to map URLs to handlers:

from pesto import Response
from pesto.dispatch import DispatcherApp
app = DispatcherApp()

recipes = {
    'pesto': "Blend garlic, oil, parmesan and pine nuts.",
    'toast': "Put bread in toaster. Toast it."

@app.match('/', 'GET')
def recipe_index(request):
    Display an index of available recipes.
    markup = ['<html><body><h1>List of recipes</h1><ul>']
    for recipe in sorted(recipes):
            '<li><a href="%s">%s</a></li>' % (
    return Response(markup)

@app.match('/recipes/<recipe:unicode>', 'GET')
def show_recipe(request, recipe):
    Display a single recipe
    if recipe not in recipes:
            return Response.not_found()

    return Response([
        '<html><body><h1>How to make %s</h1>' % recipe,
        '<p>%s</p><a href="%s">Back to index</a>' % (recipes[recipe], recipe_index.url()),

if __name__ == "__main__":
    from wsgiref import simple_server
    httpd = simple_server.make_server('', 8080, app)

Development status

Pesto is production ready and used on a wide variety of websites.

To browse or check out the latest development version, visit For documentation, visit

Mailing list

A google groups mailing list is online at Please use this for any questions or comments relating to Pesto.


Pesto is available under the terms of the new BSD licence.

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