Simple Django handlers

Or, an example about introspection targeting Python's functions.

I really like the way CherryPy maps GET parameters to the parameters of the handling function (usually, methods). I miss this mapping in Django, therefore I implemented it. I am "lazy" and I did not search Django's API for something related to this — I did this for pleasure.

Anyway, I have implemented a decorator, params_from_GET that adds this functionality to Django-handlers. You have to read the docstring to read the usage.

Code dump (licensed under public domain):

import inspect
def get_func_args(func):
    """
    Returns a generators of pairs (parameter name, default value)
    of the target function.
    """
    (args, varargs, varkw, defaults) = inspect.getargspec(func)
    if defaults is None:
        defaults = ()
    offset = len(args) - len(defaults)
    return args[:offset], dict(zip(args[offset:], defaults))

def params_from(func, method, default_value=''):
    """
    Returns a decorator, see params_from_GET.
    """
    # get the default params
    args, params = get_func_args(func)
    if args[0] != "request":
        raise TypeError("First parameters needs to be 'request'")
    for param in args[1:]:
        params[param] = default_value=''
    
    def wrapper(request, **orig_kwargs):
        # copy the parameters
        kwargs = params.copy()
        # get the map for the defined method, e.g GET
        method_dict = getattr(request, method)
        # set the request object
        kwargs['request'] = request
        for key in params:
            # fill with values that were sent by the user
            if key in method_dict:
                kwargs[key] = method_dict[key]
        kwargs.update(orig_kwargs)
        return func(**kwargs)
    return wrapper

def params_from_GET(func):
    """
    The decorator pics up a handler function and fetches the
    values from the GET map.

    For example:

    @params_from_GET
    handler(request, foo, bar):
       pass

    Is the same as:

    handler(request):
       foo = request.GET('foo', '')
       bar = request.GET('bar', '')
    """
    return params_from(func, 'GET')

Update: added support for the keyword arguments that may be passed to the dispatcher by urls.py.

Django and Unicode

I have made this patch against Django SVN r7379, please have a look at it:

--- /usr/lib/python2.5/site-packages/django/http/__init__.py    2008-03-29 22:24:02.000000000 +0000
+++ __init__.py 2008-03-29 22:23:03.000000000 +0000
@@ -360,10 +360,8 @@
         return self
 
     def next(self):
-        chunk = self._iterator.next()
-        if isinstance(chunk, unicode):
-            chunk = chunk.encode(self._charset)
-        return str(chunk)
+        chunk = unicode(self._iterator.next())
+        return chunk.encode(self._charset)
 
     def close(self):
         if hasattr(self._container, 'close'):

Before the patch, a chunk (the reply that will be sent by the HTTP server to the client) is encoded with the charset defined in our project (self._charset) only if it is an unicode object, otherwise, it will happily convert to a string using the system's encoding (by using the function str), which was resulting in a UnicodeEncodeError exception that would break Django.

If you want to make sure that the reply you are sending, through your HTTPResponse, is encoded into a string using the project's encoding, then convert it first into a unicode object. If my patch is accepted, though, this will be done automatically for you.

Oh, by the way, I am enjoying Django. I am using it to create REST web-services. It is being an enjoying and out-of-your-face experience.

Link Flood, Part 1

Um novo e interessante projecto que surgiu é o Nouveau, trata-se de uma implementação livre de drivers para placas gráficas NVidia. Tem por base o módulo do X nv e usa o programa REnouveau para, através de engenharia reversa, descobrir como a implementação proprietária funciona. Será que vamos ter umas drivers de qualidade Open Source?

Também relativo ao mundo Open Source, o projecto Django está a criar um livro, The Django Book. O contributo da comunidade é promovido através do sítio interessante onde se podem adicionar comentários, com a granularidade ao parágrafo.

O sítio NZone, da NVidia, está a disponibilizar uma demo do Cedega. Este parece um sinal que este sistema operativo o sistema operativo onde este programa corre começa a ter mais visibilidade (se bem que ínfima ainda) no mundo dos jogadores.

Uma gama de portáteis muito atraente é a Levio da marca Transtec. São muito bonitos, leves, bem artilhados, vêm com Linux e, por incrível que pareça, são baratos!