Postcard from the Pyramid view

Overview on View Lookup features

Transcript

1. Postcard from the Pyramid view Overview on View Lookup features
2. Hello, Bonjour Rach Belaid Vim Enthousiast, Python Developer, Postgres Fan, Git Lover, Belgian Erlang Hobbyist, rach @rachbelaid rachbelaid.com rachid.belaid@gmail.com
3. What are Views? Pyramid views are callable objects and can be : Function Method Class
4. Adding Views There is 2 ways to add views : - Via config method: Configurator.add_view(...) - Via decorator @view_config(...)
5. Example - add_view() from wsgiref.simple_server import make_server from pyramid.config import Configurator from pyramid.response import Response def hello_world(request): return Response('Hello world!') if __name__ == '__main__': config = Configurator() config.add_route('home', '/') config.add_view(hello_world, route_name='home') app = config.make_wsgi_app() server = make_server('0.0.0.0', 8080, app) server.serve_forever()
6. Example - view_config() from wsgiref.simple_server import make_server from pyramid.config import Configurator from pyramid.response import Response from pyramid.view import view_config @view_config(route_name='home') def hello_world(request): return Response('Hello world!') if __name__ == '__main__': config = Configurator() config.add_route('home', '/') config.scan() #run the app app = config.make_wsgi_app() server = make_server('0.0.0.0', 8080, app) server.serve_forever()
7. View ≠ Route - Routes match urls - Views match routes
8. From Request to View home profile / /username welcome welcome home welcome profile Requests Routes Views GET POST USER? GET GET Route Matching route matching View Lookup
9. View lookup ? After any routes matches “the view lookup subsystem takes over to find the most reasonable view callable for the matched route” WTF? Pyramid build a lookup resolution tree and detects conflict in the views configs. Use pviews cmd to analyse the views lookup
10. Example - Conflict detection ... def hello_world(request): return Response('Hello world!') def hi_world(request): return Response('Hello world!') if __name__ == '__main__': config = Configurator() config.add_route('home', '/') config.add_view(hello_world, route_name='home') config.add_view(hi_world, route_name='home') ... FAIL! pyramid.exceptions.ConfigurationConflictError
11. View lookup configs Pyramid allow you to configure a view to be matched using many parameters - route name - request method : POST, GET, ... - xhr - request params - match params - custom predicates function
12. Example - View Lookup route name ... def hello_world(request): return Response('Hello world!') def hi_world(request): return Response('Hello world!') if __name__ == '__main__': config = Configurator() config.add_route('test1', '/test1') config.add_route('test2', '/test2') config.add_view(hello_world, route_name='test1') config.add_view(hi_world, route_name='test2') ...
13. Example - View Lookup request method ... @view_config(route_name='test', request_method='GET') def hello_world(request): return Response('Hello world!') @view_config(route_name='test', request_method='POST') def thanks_you(request): return Response('Thanks you') if __name__ == '__main__': config = Configurator() config.add_route('test', '/test') config.scan() ...
14. Example - View Lookup Xhr ... @view_config(route_name='test') def hello_world(request): return Response('Hello world!') @view_config(route_name='test', xhr=True) def hello_world_xhr(request): val = json.dumps({'response':'Hello World'}) return Response(val) if __name__ == '__main__': config = Configurator() config.add_route('test', '/test') config.scan() ...
15. Example - View Lookup request param ... @view_config(route_name='welcome') def welcome_view(request): return Response('Hello') @view_config(route_name='welcome', request_param='submit=signup') def signup_view(request): return Response('Signup') @view_config(route_name='welcome', request_param='submit=signin') def signin_view(request): return Response('Signin') if __name__ == '__main__': config = Configurator() config.add_route('welcome', '/') config.scan() ...
16. Example - View Lookup match param ... @view_config(route_name='action', match_param='action=hello') def hello_view(request): return Response('Hello') @view_config(route_name='action', match_param='action=bye') def bye_view(request): return Response('Bye Bye') @view_config(route_name='action', match_param='action') def bye_view(request): return Response('Let’s continue') if __name__ == '__main__': config = Configurator() config.add_route('action', '/{action:\w+}') config.scan() ...
17. Example - View Lookup custom predicate ... def useless_predicate(info, request): from datetime import date today = date.today() return today.day == 29 && today.month == 2 @view_config(route_name='home', custom_predicate=useless_predicate) def useless_view(request): return Response('Leap year') if __name__ == '__main__': config = Configurator() config.add_route('home', '/') config.scan() ...
18. Others - Headers - Accept - Request Type - Context - check csrf
19. Pyramid Views: Function, Method, Class @view_config(route_name='test') def test(request): return Response('ok') Function class Test(object): def __init__(self, request): self.request = request @view_config(route_name='test') def test(self): return Response('ok') Method @view_config(route_name='test') class Test(object): def __init__(self, request): self.request = request def __call__(self): return Response('ok') Class
20. Class base views - example from ... class RESTView(object): def __init__(self, request): self.request = request @view_config(route_name='rest', request_method='GET') def get(self): return Response('get') @view_config(route_name='rest', request_method='POST') def post(self): return Response('post') @view_config(route_name='rest', request_method='DELETE') def delete(self): return Response('delete')
21. View defaults pyramid.view.view_defaults class decorator to provide defaults to the view configuration information
22. Example - view default ... @view_defaults(route_name='rest') class RESTView(object): def __init__(self, request): self.request = request @view_config(request_method='GET') def get(self): return Response('get') @view_config(request_method='POST') def post(self): return Response('post') @view_config(request_method='DELETE') def delete(self): return Response('delete')
23. Class base views - example for decorator haters @view_defaults(route_name='rest') class RESTView(object): def __init__(self, request): self.request = request def get(self): return Response('get') def post(self): return Response('post') def delete(self): return Response('delete') if __name__ == '__main__': config = Configurator() config.add_route('rest', '/rest') config.add_view(RESTView, attr='get', request_method='GET') config.add_view(RESTView, attr='post', request_method='POST') config.add_view(RESTView, attr='delete', request_method='DELETE')
24. Renderers A view don’t always need to return a Response object. If not then Pyramid attempt to use a renderer to construct a response
25. Built-in Renderers - string - JSON - JSONP - Chameleon Template : *.pt or *.txt - Mako Template : *.mak or *.mako
26. Class base views - example with renderer ... @view_defaults(route_name='rest', renderer='JSON') class RESTView(object): def __init__(self, request): self.request = request @view_config(request_method='GET') def get(self): return {'method':'GET'} @view_config(request_method='POST') def post(self): return {'method':'POST'} @view_config(request_method='DELETE') def delete(self): return {'method':'DELETE'}
27. Renderers & Templates - When the renderer is set to a Template. The view needs to return a dict to populate the context renderer='templates/home.pt' renderer='package:templates/home.mak' renderer='home.jinja2'
28. Response adapter To allow views to return objects without requiring a renderer to convert def string_response_adapter(s): response = Response(s) return response config.add_response_adapter(string_response_adapter, str)
29. 404 When Pyramid can’t map a URL to a view code, it invokes a not found view from pyramid.view import notfound_view_config @notfound_view_config() def notfound(request): return Response('Not Found, dude', status='404 Not Found') config.add_notfound_view(notfound) Or
30. 403 When Pyramid can’t authorize view based on the authorization policy, it invokes a forbidden view from pyramid.view import forbidden_view_config @forbidden_view_config() def forbidden(request): return Response('forbidden') config.add_forbidden_view(forbidden_view) Or
31. HTTP Exceptions HTTP Exceptions can be raised or returned pyramid.httpexceptions.* (200 -> 511) from pyramid.httpexceptions import HTTPNotFound, HTTPForbidden def do_something_notfound(request): return HTTPNotFound() def do_something_forbidden(request): raise HTTPForbidden()
32. Static view Pyramid makes it possible to serve up static asset files from a directory on a filesystem The name represents a URL prefix config.add_static_view(name='static', path='/var/www/static')
33. Missing the good old days? - You can attach view directly to a route config.add_route('home', '/', view= function_view) - You can event use Python dotted name config.add_route('home', '/', view= 'module.function_view')
34. So much more! Events Tweens View predicates Subscriber predicates Callbacks View Mapper Pviews cmd Renderer adapter