The starter files generated by the
are basic, but they provide a good orientation for the high-level
patterns common to most url dispatch -based Pyramid
The source code for this tutorial stage can be browsed at http://github.com/Pylons/pyramid/tree/1.0-branch/docs/tutorials/wiki2/src/basiclayout/.
App Startup with
A directory on disk can be turned into a Python package by containing
__init__.py file. Even if empty, this marks a directory as a Python
package. We use
__init__.py both as a package marker and to contain
development.ini file is read by
paster which looks for
the application module in the
use variable of the
section. The entry point is defined in the Setuptools configuration of this
module, specifically in the
setup.py file. For this tutorial, the entry
point is defined as
tutorial:main and points to the following
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 from pyramid.config import Configurator from sqlalchemy import engine_from_config from tutorial.models import initialize_sql def main(global_config, **settings): """ This function returns a Pyramid WSGI application. """ engine = engine_from_config(settings, 'sqlalchemy.') initialize_sql(engine) config = Configurator(settings=settings) config.add_static_view('static', 'tutorial:static') config.add_route('home', '/', view='tutorial.views.my_view', view_renderer='templates/mytemplate.pt') return config.make_wsgi_app()
- Lines 1-4. Imports to support later code.
- Line 9. Create a SQLAlchemy database engine from the
sqlalchemy.prefixed settings in the
[app:tutorial]section. This will be a URI (something like
- Line 10. We initialize our SQL database using SQLAlchemy, passing it the engine
- Line 11. We construct a Configurator.
settingsis passed as a keyword argument with the dictionary values passed by PasteDeploy as the
settingsargument. This will be a dictionary of settings parsed by PasteDeploy, which contains deployment-related values such as
- Line 12. We call
pyramid.config.Configurator.add_static_view()with the arguments
static(the name), and
tutorial:static(the path). This registers a static resource view which will match any URL that starts with
/static/. This will serve up static resources for us from within the
staticdirectory of our
tutorialpackage, in this case, via
http://localhost:6543/static/and below. With this declaration, we’re saying that any URL that starts with
/staticshould go to the static view; any remainder of its path (e.g. the
/static/foo) will be used to compose a path to a static file resource, such as a CSS file.
- Lines 13-14. Register a route configuration via the
pyramid.config.Configurator.add_route()method that will be used when the URL is
/. Since this route has a
/it is the “default” route. The argument named
viewwith the value
tutorial.views.my_viewis the dotted name to a function we write (generated by the
pyramid_routesalchemytemplate) that is given a
requestobject and which returns a response or a dictionary. You will use
pyramid.config.Configurator.add_route()statements in a URL dispatch based application to map URLs to code. This route also names a
view_renderer, which is a template which lives in the
templatessubdirectory of the package. When the
tutorial.views.my_viewview returns a dictionary, a renderer will use this template to create a response.
- Line 15. We use the
pyramid.config.Configurator.make_wsgi_app()method to return a WSGI application.
Content Models with
In a SQLAlchemy-based application, a model object is an object
composed by querying the SQL database which backs an application.
SQLAlchemy is an “object relational mapper” (an ORM). The
models.py file is where the
template put the classes that implement our models.
Here is the source for
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 import transaction from sqlalchemy import Column from sqlalchemy import Integer from sqlalchemy import Unicode from sqlalchemy.exc import IntegrityError from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import scoped_session from sqlalchemy.orm import sessionmaker from zope.sqlalchemy import ZopeTransactionExtension DBSession = scoped_session(sessionmaker( extension=ZopeTransactionExtension())) Base = declarative_base() class MyModel(Base): __tablename__ = 'models' id = Column(Integer, primary_key=True) name = Column(Unicode(255), unique=True) value = Column(Integer) def __init__(self, name, value): self.name = name self.value = value def populate(): session = DBSession() model = MyModel(name=u'root',value=55) session.add(model) session.flush() transaction.commit() def initialize_sql(engine): DBSession.configure(bind=engine) Base.metadata.bind = engine Base.metadata.create_all(engine) try: populate() except IntegrityError: pass
- Lines 1-13. Imports to support later code.
- Line 15. We set up a SQLAlchemy “DBSession” object here. We specify that we’d like to use the “ZopeTransactionExtension”. This extension is an extension which allows us to use a transaction manager instead of controlling commits and aborts to database operations by hand.
- Line 16. We create a declarative
Baseobject to use as a base class for our model.
- Lines 18-26. A model class named
MyModel. It has an
__init__that takes a two arguments (
value). It stores these values as
__init__function itself. The
MyModelclass also has a
__tablename__attribute. This informs SQLAlchemy which table to use to store the data representing instances of this class.
- Lines 28-33. A function named
populatewhich adds a single model instance into our SQL storage and commits a transaction.
- Lines 35-42. A function named
initialize_sqlwhich receives a SQL database engine and binds it to our SQLAlchemy DBSession object. It also calls the
populatefunction, to do initial database population.