[Stackless] [ANN] Nagare 0.3.0 - Components and continuation-based web framework

Alain Poirier alain.poirier at net-ng.com
Tue Feb 16 18:27:06 CET 2010

Hi all,

The version 0.3.0 of the Nagare web framework is now released !

To read about its features:

Release info and download page:

Release info and download page of the examples:

Source and documentation available at the website:

Mailing lists - the place to ask questions:

About Nagare

Nagare is a components based framework: a Nagare application
is a composition of interacting components each one with its
own state and workflow kept on the server. Each component
can have one or several views that are composed to generate
the final web page. This enables the developers to reuse or
write highly reusable components easily and quickly.

Thanks to Stackless Python, Nagare is also a continuation-based
web framework which enables to code a web application like a
desktop application, with no need to split its control flow in
a multitude of controllers and with the automatic handling of
the back, fork and refresh actions from the browser.

Its component model and use of the continuation come from the
famous Seaside Smalltalk framework.

Furthermore Nagare integrates the best tools and standard from
the Python world. For example:

  - WSGI: binds the application to several possible publishers,
  - lxml: generates the DOM trees and brings to Nagare the full
    set of XML features (XSL, XPath, Schemas ...),
  - setuptools: installs, deploys and extends the Nagare framework
    and the Nagare applications too,
  - PEAK Rules: generic methods are heavily used in Nagare, to
    associate views to components, to define security rules, to
    translate Python code to Javascript ...
  - WebOb: for its Request and Response Objects.


A complete "guess a number" game to taste how easy web coding
becomes using continuations:

  import random
  from nagare import component, util

  class Number(component.Task):
      """A little game to guess a number
      def go(self, comp):
	  """The game algorithm, using continuation for a pure linear Python code
	    - ``comp`` -- this component
	  self.attempt = 1
	  number = random.randint(1, 20)
	  comp.call(util.Confirm('I choose a number between 1 and 20. Try to guess it'))
	  while True:
	      x = comp.call(util.Ask('Try #%d: ' % self.attempt))
	      if not x.isdigit():
	      x = int(x)
	      if x > number:
		  comp.call(util.Confirm('Choose a lower number'))
	      if x < number:
		  comp.call(util.Confirm('Choose a greater number'))
	      if x == number:
		  comp.call(util.Confirm('You guessed the number in %d attempts' % self.attempt))

	      self.attempt += 1

A simple todo list, illustrating the programmatic HTML generation,
the association of view(s) to Python objects and the direct association
of callbacks to HTML form elements and links:

    from nagare import presentation
    from nagare.namespaces import xhtml

    # A plain Python ``TodoList`` class
    class TodoList(object):
	def __init__(self):
	    self.todo = []

	def add_todo(self, msg):

    # The default HTML view, generated in programmatic HTML
    def render(self, h, comp, model):
        # ``h`` is a (X)HTML renderer (http://www.nagare.org/trac/wiki/RendererObjects)
	with h.div:
	    for msg in self.todo:
		h << h.blockquote(msg) << h.hr

	with h.form:
	    h << 'New todo:' << h.br
	    h << h.textarea.action(self.add_todo) << h.br
	    h << h.input(type='submit', value='Add')

	return h.root

0.3.0 Changelog

New features

  - refactoring of the sessions managers:

    - session objects now keep track of their sessions manager
    - no more sessions manager factories
    - configurable pickler / unpickler objects
    - configuration switch ``states_history`` to set if an objects graphs history must be kept
    - new sessions manager (``type=memory``) that keeps the objects graphs in memory, without any pickling
  - logging service added:

    - one dedicated logger for each published applications is created
    - easy configuration and use of this dedicated logger
    - all the ``[logging]`` sections of all the published applications are merged before to configure the Python logging system
  - preliminary Comet support added (currently only working in a multi-threaded env.)
  - last exception raised kept by the ``WSGIApp`` objects and exception hook added
  - ``with_request`` parameter added to all the callback registrations and ``Update()`` objects
  - translation of Python modules to Javascript added
  - configurable name for the security cookie (one of the post Nagare security audit actions)
  - configuration of the ``WSGIApp`` objects split accross multiples `set_*`` methods
  - ``get_registered_applications()`` added to the publisher objects
  - full YUI bundled with Nagare
  - New versions:

    - Stackless Python 2.6.4 is now the recommanded Python version
    - virtualenv updated to 1.4.5
    - SQLAlchemy updated to 0.5.8
    - Elixir updated to 0.7.1
    - Lxml updated to 2.2.4
    - YUI updated to 2.8.0r4


  - with the YUI connection manager, a large browser response must be reassembled (Firefox only)
  - late creation of the SQLAlchemy database engines and metadatas binding
  - input fields ot type ``button`` now working in an Ajax submit
  - ``Var.var()`` now working inn a unicode context
  - ``nagare-admin create-rules`` had problems when a static directory didn't exist
  - bad boolean expressions parenthesis translation in pyjs fixed
  - parsing (X)HTML from URL now working under Windows

Bugs fixed

  - #47: ``set_publisher()`` called when using "nagare-admin create-db"
  - #48: py2js parentheses bug
  - #49: ``reset`` configuration ignored by the memcached sessions manager
  - #50: [log] inferred caller is wrong


A. Poirier

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