declarative class expressinons

routeclass.py

# Using class expressions for declarative programming in python
import inspect

def route(path, func, *methods):
    '''
    An example on how to create function usable for
    declarative programming in python. These functions
    will sit on the class body and setup some state for
    latter use.
    
    Since we are in the class body the class wasn't declared
    yet, so we can't modify it. Instead we hold the declaration in
    another place so that we can retrieve latter. In this
    example I'm saving the declarations inside the function as
    a attribute.

    Suppose that we have a webframework and we want to declare
    routes this way:
    >>> class Routes:
    ...     route('/foo', lambda:200, 'POST', 'GET')
    ...     route('/bar', lambda:403, 'DELETE')


    This function will save all the calls to route.routes attribute
    during the class parsing time. They can be fetched after the class was
    parsed.

    To retrieve the first route path we can do
    >>> route.routes['Routes'][0]['path'] # The first route call path
    '/foo'

    The class name is saved within `classname` key, the same approach
    can be used to retrieve the qualified name of the class with package
    and module name.
    '''
    clsname = inspect.currentframe().f_back.f_code.co_name
    route.routes.setdefault(clsname, []).append(dict(classname=clsname, path=path, func=func, methods=methods))
route.routes = {}


if __name__ == '__main__':
    import doctest
    doctest.testmod()