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.