25 avril 2011


I started implementing a set of utility commands to manipulate a Jackrabbit content repository from the Symfony2 command console.

The code is on github.

Python MiniMVC

Going further with the concepts exposed in my last post I coded a basic Micro framework for Python running above mod_python for Apache.

MiniMVC is a Python micro MVC framework inspired by Symfony2 from the PHP world.

MiniMVC is lightweighted
MiniMVC uses dependency injection
MiniMVC is configured with YAML
MiniMVC is tested (partially)

MiniMVC features:

A configurable service container
A flexible and configurable request router based on pyroutes
Powerful logging mechanism based on logbook
Basic SQL Alchemy binding
Cheetah and Mako templates, new templating engines can be added very easily


Don't render the content files through the kernel
Write more tests
Reorganize imports
Configure SQLAlchemy with the ServiceContainer
Generate table classes
Generate entities
Read XML configuration in addition to yaml
More templating engines

You can find the code on github.

10 avril 2011

A very simple HTTP server with basic MVC in Python

This is a simple proof of concept of a very simple HTTP server implementing a very basic MVC model (actually only routing and controller) in Python.

We will use the BaseHTTPServer as the web server.

The controller base class

All the controller needs is a reference to the BaseHTTPServer so that it can access the web request and write out the response.

class Controller(object):

    def __init__(self, server):
        self.__server = server

    def server(self):
        return self.__server

The router

The router needs to manipulate the request and response but also instanciate the controllers, that is why it receives an instance of BaseHTTPServer.

The routes are defined by 3 components:

- A regular expression that must be matched to trigger the route
- A controller class to be instanciated
- A method name to be called on the controller

The tricky part here is to instanciate the controller and call a method on it.

class Router(object):

    def __init__(self, server):
        self.__routes = []
        self.__server = server

    def addRoute(self, regexp, controller, action):
        self.__routes.append({'regexp': regexp, 'controller': controller, 'action': action})
    def route(self, path):
        for route in self.__routes:
            if re.search(route['regexp'], path):
                cls = globals()[route['controller']]
                func = cls.__dict__[route['action']]
                obj = cls(self.__server)
                apply(func,(obj, ))

        # Not found

The request handler

All the request handler needs to do is to instanciate the Router and add to it the routes it needs to manage.

This simple request handler is only able to reply to GET requests.

class MyRequestHandler(BaseHTTPRequestHandler):

    def __init__(self, request, client_address, server):
        routes = [
            {'regexp': r'^/$', 'controller': 'HomeController', 'action': 'indexAction'},
            {'regexp': r'^/content/', 'controller': 'ContentController', 'action': 'showAction'}
        self.__router = Router(self)
        for route in routes:
            self.__router.addRoute(route['regexp'], route['controller'], route['action'])

        BaseHTTPRequestHandler.__init__(self, request, client_address, server)
    def do_GET(self):

A simple Hello World controller

class HomeController(Controller):

    def __init__(self, server):
        Controller.__init__(self, server)

    def indexAction(self):
        self.server.send_header('Content-type', 'text/html')
        self.server.wfile.write('Hello world')

By the way, in MVC a controller should not do View stuff, see "Going further with a templating engine" below to make the separation better using a view layer.

A controller rendering a file

This controller will serve a file in the "public/" directory. Be carefull there is not enough error checking in this code...

class ContentController(Controller):
    CONTENT_BASE_PATH = 'public/'

    def __init__(self, server):
        Controller.__init__(self, server)
    def showAction(self):
        filename = ContentController.CONTENT_BASE_PATH + self.server.path[9:]
        if os.access(filename, os.R_OK) and not os.path.isdir(filename):
            #TODO: is there any possibility to access files outside the root with ..?
            file = open(filename, "r")
            content = file.read()
            #TODO: set correct content type
            self.server.send_header('Content-type', 'text/html')

Running the server

What we have defined here is a simple http server that will reply "Hello world" when the URL "/" is accessed, and return the content of a file named myFile (if it exists) when the URL "/content/myFile" is reached.

def main():
        httpd = HTTPServer(('', 8000), MyRequestHandler)
        print 'Server started...'
 print 'Server shutting down'

if __name__ == '__main__':

Going further with a templating engine

It is quite simple to integrate a templating engine like Cheetah in this code.

Here is a example of controller rendering a template:

class TemplateController(Controller):

    def __init__(self, server):
        Controller.__init__(self, server)

    def listAction(self):
        self.server.send_header('Content-type', 'text/html')
        self.server.wfile.write(Template ( file = 'templates/hello_world.tmpl', searchList = [{ }] ))


That's the reason why I love Python so much, in very few lines we could implement basic MVC over a simple web server.