.. _quick_tour:
=====================
Quick Tour of Pyramid
=====================
Pyramid lets you start small and finish big. This *Quick Tour* of Pyramid is
for those who want to evaluate Pyramid, whether you are new to Python
web frameworks, or a pro in a hurry. For more detailed treatment of
each topic, give the :ref:`quick_tutorial` a try.
Installation
============
Once you have a standard Python environment setup, getting started with
Pyramid is a breeze. Unfortunately "standard" is not so simple in Python.
For this Quick Tour, it means: `Python `_,
a `virtual environment `_ (or
`virtualenv for Python 2.7 `_), and
`setuptools `_.
As an example, for Python 3.3+ on Linux:
.. parsed-literal::
$ pyvenv env33
$ wget https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py -O - | env33/bin/python
$ env33/bin/easy_install "pyramid==\ |release|\ "
For Windows:
.. parsed-literal::
# Use your browser to download:
# https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py
c:\\> c:\\Python33\\python -m venv env33
c:\\> env33\\Scripts\\python ez_setup.py
c:\\> env33\\Scripts\\easy_install "pyramid==\ |release|\ "
Of course Pyramid runs fine on Python 2.6+, as do the examples in this
*Quick Tour*. We're just showing Python 3 a little love (Pyramid had
production support for Python 3 in October 2011).
.. note::
Why ``easy_install`` and not ``pip``? Some distributions on which Pyramid
depends upon have optional C extensions for performance. ``pip`` cannot
install some binary Python distributions. With ``easy_install``, Windows
users are able to obtain binary Python distributions, so they get the
benefit of the C extensions without needing a C compiler. Also, there can
be issues when ``pip`` and ``easy_install`` are used side-by-side in the
same environment, so we chose to recommend ``easy_install`` for the sake of
reducing the complexity of these instructions.
.. seealso:: See also:
:ref:`Quick Tutorial section on Requirements `,
:ref:`installing_unix`,
:ref:`Before You Install `, and
:ref:`Installing Pyramid on a Windows System `
Hello World
===========
Microframeworks have shown that learning starts best from a very small
first step. Here's a tiny application in Pyramid:
.. literalinclude:: quick_tour/hello_world/app.py
:linenos:
This simple example is easy to run. Save this as ``app.py`` and run it:
.. code-block:: bash
$ python ./app.py
Next open http://localhost:6543/ in a browser, and you will see the ``Hello
World!`` message.
New to Python web programming? If so, some lines in the module merit
explanation:
#. *Line 10*. The ``if __name__ == '__main__':`` is Python's way of
saying "Start here when running from the command line".
#. *Lines 11-13*. Use Pyramid's :term:`configurator` to connect
:term:`view` code to a particular URL :term:`route`.
#. *Lines 6-7*. Implement the view code that generates the
:term:`response`.
#. *Lines 14-16*. Publish a :term:`WSGI` app using an HTTP server.
As shown in this example, the :term:`configurator` plays a central role
in Pyramid development. Building an application from loosely-coupled
parts via :doc:`../narr/configuration` is a central idea in Pyramid,
one that we will revisit regurlarly in this *Quick Tour*.
.. seealso:: See also:
:ref:`Quick Tutorial Hello World `,
:ref:`firstapp_chapter`, and
:ref:`Todo List Application in One File `
Handling web requests and responses
===================================
Developing for the web means processing web requests. As this is a
critical part of a web application, web developers need a robust,
mature set of software for web requests.
Pyramid has always fit nicely into the existing world of Python web
development (virtual environments, packaging, scaffolding, one of the first to
embrace Python 3, etc.). Pyramid turned to the well-regarded :term:`WebOb`
Python library for request and response handling. In our example above,
Pyramid hands ``hello_world`` a ``request`` that is :ref:`based on WebOb
`.
Let's see some features of requests and responses in action:
.. literalinclude:: quick_tour/requests/app.py
:pyobject: hello_world
In this Pyramid view, we get the URL being visited from ``request.url``. Also,
if you visited http://localhost:6543/?name=alice in a browser, the name is
included in the body of the response::
URL http://localhost:6543/?name=alice with name: alice
Finally, we set the response's content type and return the Response.
.. seealso:: See also:
:ref:`Quick Tutorial Request and Response `
and
:ref:`webob_chapter`
Views
=====
For the examples above, the ``hello_world`` function is a "view". In
Pyramid, views are the primary way to accept web requests and return
responses.
So far our examples place everything in one file:
- the view function
- its registration with the configurator
- the route to map it to an URL
- the WSGI application launcher
Let's move the views out to their own ``views.py`` module and change
the ``app.py`` to scan that module, looking for decorators that set up
the views.
First, our revised ``app.py``:
.. literalinclude:: quick_tour/views/app.py
:linenos:
We added some more routes, but we also removed the view code.
Our views and their registrations (via decorators) are now in a module
``views.py``, which is scanned via ``config.scan('views')``.
We now have a ``views.py`` module that is focused on handling requests
and responses:
.. literalinclude:: quick_tour/views/views.py
:linenos:
We have four views, each leading to the other. If you start at
http://localhost:6543/, you get a response with a link to the next
view. The ``hello_view`` (available at the URL ``/howdy``) has a link
to the ``redirect_view``, which issues a redirect to the final
view.
Earlier we saw ``config.add_view`` as one way to configure a view. This
section introduces ``@view_config``. Pyramid's configuration supports
:term:`imperative configuration`, such as the ``config.add_view`` in
the previous example. You can also use :term:`declarative
configuration`, in which a Python :term:`decorator` is placed on the
line above the view. Both approaches result in the same final
configuration, thus usually it is simply a matter of taste.
.. seealso:: See also:
:ref:`Quick Tutorial Views `,
:doc:`../narr/views`,
:doc:`../narr/viewconfig`, and
:ref:`debugging_view_configuration`
Routing
=======
Writing web applications usually means sophisticated URL design. We
just saw some Pyramid machinery for requests and views. Let's look at
features that help in routing.
Above we saw the basics of routing URLs to views in Pyramid:
- Your project's "setup" code registers a route name to be used when
matching part of the URL
- Elsewhere a view is configured to be called for that route name
.. note::
Why do this twice? Other Python web frameworks let you create a
route and associate it with a view in one step. As
illustrated in :ref:`routes_need_ordering`, multiple routes might
match the same URL pattern. Rather than provide ways to help guess,
Pyramid lets you be explicit in ordering. Pyramid also gives
facilities to avoid the problem.
What if we want part of the URL to be available as data in my view? This
route declaration:
.. literalinclude:: quick_tour/routing/app.py
:start-after: Start Route 1
:end-before: End Route 1
With this, URLs such as ``/howdy/amy/smith`` will assign ``amy`` to
``first`` and ``smith`` to ``last``. We can then use this data in our
view:
.. literalinclude:: quick_tour/routing/views.py
:start-after: Start Route 1
:end-before: End Route 1
``request.matchdict`` contains values from the URL that match the
"replacement patterns" (the curly braces) in the route declaration.
This information can then be used in your view.
.. seealso:: See also:
:ref:`Quick Tutorial Routing `,
:doc:`../narr/urldispatch`,
:ref:`debug_routematch_section`, and
:doc:`../narr/router`
Templating
==========
Ouch. We have been making our own ``Response`` and filling the response
body with HTML. You usually won't embed an HTML string directly in
Python, but instead, will use a templating language.
Pyramid doesn't mandate a particular database system, form library,
etc. It encourages replaceability. This applies equally to templating,
which is fortunate: developers have strong views about template
languages. That said, the Pylons Project officially supports bindings for
Chameleon, Jinja2, and Mako, so in this step, let's use Chameleon.
Let's add ``pyramid_chameleon``, a Pyramid :term:`add-on` which enables
Chameleon as a :term:`renderer` in our Pyramid applications:
.. code-block:: bash
$ easy_install pyramid_chameleon
With the package installed, we can include the template bindings into
our configuration:
.. code-block:: python
config.include('pyramid_chameleon')
Now lets change our views.py file:
.. literalinclude:: quick_tour/templating/views.py
:start-after: Start View 1
:end-before: End View 1
Ahh, that looks better. We have a view that is focused on Python code.
Our ``@view_config`` decorator specifies a :term:`renderer` that points
to our template file. Our view then simply returns data which is then
supplied to our template:
.. literalinclude:: quick_tour/templating/hello_world.pt
:language: html
Since our view returned ``dict(name=request.matchdict['name'])``,
we can use ``name`` as a variable in our template via
``${name}``.
.. seealso:: See also:
:ref:`Quick Tutorial Templating `,
:doc:`../narr/templates`,
:ref:`debugging_templates`, and
:ref:`available_template_system_bindings`
Templating with ``jinja2``
==========================
We just said Pyramid doesn't prefer one templating language over
another. Time to prove it. Jinja2 is a popular templating system,
modeled after Django's templates. Let's add ``pyramid_jinja2``,
a Pyramid :term:`add-on` which enables Jinja2 as a :term:`renderer` in
our Pyramid applications:
.. code-block:: bash
$ easy_install pyramid_jinja2
With the package installed, we can include the template bindings into
our configuration:
.. code-block:: python
config.include('pyramid_jinja2')
The only change in our view is to point the renderer at the ``.jinja2`` file:
.. literalinclude:: quick_tour/jinja2/views.py
:start-after: Start View 1
:end-before: End View 1
Our Jinja2 template is very similar to our previous template:
.. literalinclude:: quick_tour/jinja2/hello_world.jinja2
:language: html
Pyramid's templating add-ons register a new kind of renderer into your
application. The renderer registration maps to different kinds of
filename extensions. In this case, changing the extension from ``.pt``
to ``.jinja2`` passed the view response through the ``pyramid_jinja2``
renderer.
.. seealso:: See also:
:ref:`Quick Tutorial Jinja2 `,
`Jinja2 homepage `_, and
:ref:`pyramid_jinja2 Overview `
Static assets
=============
Of course the Web is more than just markup. You need static assets:
CSS, JS, and images. Let's point our web app at a directory where
Pyramid will serve some static assets. First another call to the
:term:`configurator`:
.. literalinclude:: quick_tour/static_assets/app.py
:start-after: Start Static 1
:end-before: End Static 1
This tells our WSGI application to map requests under
http://localhost:6543/static/ to files and directories inside a
``static`` directory alongside our Python module.
Next make a directory named ``static``, and place ``app.css`` inside:
.. literalinclude:: quick_tour/static_assets/static/app.css
:language: css
All we need to do now is point to it in the ```` of our Jinja2
template:
.. literalinclude:: quick_tour/static_assets/hello_world.pt
:language: html
:start-after: Start Link 1
:end-before: End Link 1
This link presumes that our CSS is at a URL starting with ``/static/``.
What if the site is later moved under ``/somesite/static/``? Or perhaps
a web developer changes the arrangement on disk? Pyramid provides a helper
to allow flexibility on URL generation:
.. literalinclude:: quick_tour/static_assets/hello_world.pt
:language: html
:start-after: Start Link 2
:end-before: End Link 2
By using ``request.static_url`` to generate the full URL to the static
assets, you both ensure you stay in sync with the configuration and
gain refactoring flexibility later.
.. seealso:: See also:
:ref:`Quick Tutorial Static Assets `,
:doc:`../narr/assets`,
:ref:`preventing_http_caching`, and
:ref:`influencing_http_caching`
Returning JSON
==============
Modern web apps are more than rendered HTML. Dynamic pages now use
JavaScript to update the UI in the browser by requesting server data as
JSON. Pyramid supports this with a JSON renderer:
.. literalinclude:: quick_tour/json/views.py
:start-after: Start View 1
:end-before: End View 2
This wires up a view that returns some data through the JSON
:term:`renderer`, which calls Python's JSON support to serialize the data
into JSON and set the appropriate HTTP headers.
.. seealso:: See also:
:ref:`Quick Tutorial JSON `,
:ref:`views_which_use_a_renderer`,
:ref:`json_renderer`, and
:ref:`adding_and_overriding_renderers`
View classes
============
So far our views have been simple, free-standing functions. Many times
your views are related: different ways to look at or work on the same
data, or a REST API that handles multiple operations. Grouping these
together as a :ref:`view class ` makes sense.
- Group views
- Centralize some repetitive defaults
- Share some state and helpers
The following shows a "Hello World" example with three operations: view
a form, save a change, or press the delete button:
.. literalinclude:: quick_tour/view_classes/views.py
:start-after: Start View 1
:end-before: End View 1
As you can see, the three views are logically grouped together.
Specifically:
- The first view is returned when you go to ``/howdy/amy``. This URL is
mapped to the ``hello`` route that we centrally set using the optional
``@view_defaults``.
- The second view is returned when the form data contains a field with
``form.edit``, such as clicking on
````. This rule
is specified in the ``@view_config`` for that view.
- The third view is returned when clicking on a button such
as ````.
Only one route is needed, stated in one place atop the view class. Also,
the assignment of ``name`` is done in the ``__init__`` function. Our
templates can then use ``{{ view.name }}``.
Pyramid view classes, combined with built-in and custom predicates,
have much more to offer:
- All the same view configuration parameters as function views
- One route leading to multiple views, based on information in the
request or data such as ``request_param``, ``request_method``,
``accept``, ``header``, ``xhr``, ``containment``, and
``custom_predicates``
.. seealso:: See also:
:ref:`Quick Tutorial View Classes `,
:ref:`Quick Tutorial More View Classes `, and
:ref:`class_as_view`
Quick project startup with scaffolds
====================================
So far we have done all of our *Quick Tour* as a single Python file. No Python
packages, no structure. Most Pyramid projects, though, aren't developed this
way.
To ease the process of getting started, Pyramid provides *scaffolds* that
generate sample projects from templates in Pyramid and Pyramid add-ons.
Pyramid's ``pcreate`` command can list the available scaffolds:
.. code-block:: bash
$ pcreate --list
Available scaffolds:
alchemy: Pyramid SQLAlchemy project using url dispatch
pyramid_jinja2_starter: Pyramid Jinja2 starter project
starter: Pyramid starter project
zodb: Pyramid ZODB project using traversal
The ``pyramid_jinja2`` add-on gave us a scaffold that we can use. From the
parent directory of where we want our Python package to be generated, let's use
that scaffold to make our project:
.. code-block:: bash
$ pcreate --scaffold pyramid_jinja2_starter hello_world
We next use the normal Python command to set up our package for development:
.. code-block:: bash
$ cd hello_world
$ python ./setup.py develop
We are moving in the direction of a full-featured Pyramid project, with a
proper setup for Python standards (packaging) and Pyramid configuration. This
includes a new way of running your application:
.. code-block:: bash
$ pserve development.ini
Let's look at ``pserve`` and configuration in more depth.
.. seealso:: See also:
:ref:`Quick Tutorial Scaffolds `,
:ref:`project_narr`, and
:doc:`../narr/scaffolding`
Application running with ``pserve``
===================================
Prior to scaffolds, our project mixed a number of operational details into our
code. Why should my main code care which HTTP server I want and what port
number to run on?
``pserve`` is Pyramid's application runner, separating operational details from
your code. When you install Pyramid, a small command program called ``pserve``
is written to your ``bin`` directory. This program is an executable Python
module. It's very small, getting most of its brains via import.
You can run ``pserve`` with ``--help`` to see some of its options. Doing so
reveals that you can ask ``pserve`` to watch your development files and reload
the server when they change:
.. code-block:: bash
$ pserve development.ini --reload
The ``pserve`` command has a number of other options and operations. Most of
the work, though, comes from your project's wiring, as expressed in the
configuration file you supply to ``pserve``. Let's take a look at this
configuration file.
.. seealso:: See also:
:ref:`what_is_this_pserve_thing`
Configuration with ``.ini`` files
=================================
Earlier in *Quick Tour* we first met Pyramid's configuration system. At that
point we did all configuration in Python code. For example, the port number
chosen for our HTTP server was right there in Python code. Our scaffold has
moved this decision and more into the ``development.ini`` file:
.. literalinclude:: quick_tour/package/development.ini
:language: ini
Let's take a quick high-level look. First the ``.ini`` file is divided into
sections:
- ``[app:main]`` configures our WSGI app
- ``[server:main]`` holds our WSGI server settings
- Various sections afterwards configure our Python logging system
We have a few decisions made for us in this configuration:
#. *Choice of web server:* ``use = egg:hello_world`` tells ``pserve`` to
use the ``waitress`` server.
#. *Port number:* ``port = 6543`` tells ``waitress`` to listen on port 6543.
#. *WSGI app:* What package has our WSGI application in it?
``use = egg:hello_world`` in the app section tells the configuration what
application to load.
#. *Easier development by automatic template reloading:* In development mode,
you shouldn't have to restart the server when editing a Jinja2 template.
``pyramid.reload_templates = true`` sets this policy, which might be
different in production.
Additionally the ``development.ini`` generated by this scaffold wired up
Python's standard logging. We'll now see in the console, for example, a log on
every request that comes in, as well as traceback information.
.. seealso:: See also:
:ref:`Quick Tutorial Application Configuration `,
:ref:`environment_chapter` and
:doc:`../narr/paste`
Easier development with ``debugtoolbar``
========================================
As we introduce the basics, we also want to show how to be productive in
development and debugging. For example, we just discussed template reloading
and earlier we showed ``--reload`` for application reloading.
``pyramid_debugtoolbar`` is a popular Pyramid add-on which makes several tools
available in your browser. Adding it to your project illustrates several points
about configuration.
The scaffold ``pyramid_jinja2_starter`` is already configured to include the
add-on ``pyramid_debugtoolbar`` in its ``setup.py``:
.. literalinclude:: quick_tour/package/setup.py
:language: python
:linenos:
:lineno-start: 11
:lines: 11-16
It was installed when you previously ran:
.. code-block:: bash
$ python ./setup.py develop
The ``pyramid_debugtoolbar`` package is a Pyramid add-on, which means we need
to include its configuration into our web application. The ``pyramid_jinja2``
add-on already took care of this for us in its ``__init__.py``:
.. literalinclude:: quick_tour/package/hello_world/__init__.py
:language: python
:linenos:
:lineno-start: 16
:lines: 19
And it uses the ``pyramid.includes`` facility in our ``development.ini``:
.. literalinclude:: quick_tour/package/development.ini
:language: ini
:linenos:
:lineno-start: 15
:lines: 15-16
You'll now see a Pyramid logo on the right side of your browser window, which
when clicked opens a new window that provides introspective access to debugging
information. Even better, if your web application generates an error, you will
see a nice traceback on the screen. When you want to disable this toolbar,
there's no need to change code: you can remove it from ``pyramid.includes`` in
the relevant ``.ini`` configuration file.
.. seealso:: See also:
:ref:`Quick Tutorial pyramid_debugtoolbar ` and
:ref:`pyramid_debugtoolbar `
Unit tests and ``nose``
=======================
Yikes! We got this far and we haven't yet discussed tests. This is particularly
egregious, as Pyramid has had a deep commitment to full test coverage since
before its release.
Our ``pyramid_jinja2_starter`` scaffold generated a ``tests.py`` module with
one unit test in it. To run it, let's install the handy ``nose`` test runner by
editing ``setup.py``. While we're at it, we'll throw in the ``coverage`` tool
which yells at us for code that isn't tested. Edit line 36 so it becomes the
following:
.. code-block:: python
:linenos:
:lineno-start: 36
tests_require={
'testing': ['nose', 'coverage'],
},
We changed ``setup.py`` which means we need to rerun
``python ./setup.py develop``. We can now run all our tests:
.. code-block:: bash
$ nosetests hello_world/tests.py
.
Name Stmts Miss Cover Missing
---------------------------------------------------
hello_world 11 8 27% 11-23
hello_world.models 5 1 80% 8
hello_world.tests 14 0 100%
hello_world.views 4 0 100%
---------------------------------------------------
TOTAL 34 9 74%
----------------------------------------------------------------------
Ran 1 test in 0.009s
OK
Our unit test passed. What did our test look like?
.. literalinclude:: quick_tour/package/hello_world/tests.py
:linenos:
Pyramid supplies helpers for test writing, which we use in the test setup and
teardown. Our one test imports the view, makes a dummy request, and sees if the
view returns what we expected.
.. seealso:: See also:
:ref:`Quick Tutorial Unit Testing `, :ref:`Quick
Tutorial Functional Testing `, and
:ref:`testing_chapter`
Logging
=======
It's important to know what is going on inside our web application. In
development we might need to collect some output. In production we might need
to detect situations when other people use the site. We need *logging*.
Fortunately Pyramid uses the normal Python approach to logging. The scaffold
generated in your ``development.ini`` has a number of lines that configure the
logging for you to some reasonable defaults. You then see messages sent by
Pyramid (for example, when a new request comes in).
Maybe you would like to log messages in your code? In your Python module,
import and set up the logging:
.. literalinclude:: quick_tour/package/hello_world/views.py
:language: python
:linenos:
:lineno-start: 3
:lines: 3-4
You can now, in your code, log messages:
.. literalinclude:: quick_tour/package/hello_world/views.py
:language: python
:linenos:
:lineno-start: 9
:lines: 9-10
:emphasize-lines: 2
This will log ``Some Message`` at a ``debug`` log level to the
application-configured logger in your ``development.ini``. What controls that?
These emphasized sections in the configuration file:
.. literalinclude:: quick_tour/package/development.ini
:language: ini
:linenos:
:lineno-start: 36
:lines: 36-52
:emphasize-lines: 1-2,14-17
Our application, a package named ``hello_world``, is set up as a logger and
configured to log messages at a ``DEBUG`` or higher level. When you visit
http://localhost:6543, your console will now show::
2016-01-18 13:55:55,040 DEBUG [hello_world.views:10][waitress] Some Message
.. seealso:: See also:
:ref:`Quick Tutorial Logging ` and :ref:`logging_chapter`.
Sessions
========
When people use your web application, they frequently perform a task that
requires semi-permanent data to be saved. For example, a shopping cart. This is
called a :term:`session`.
Pyramid has basic built-in support for sessions. Third party packages such as
``pyramid_redis_sessions`` provide richer session support. Or you can create
your own custom sessioning engine. Let's take a look at the :doc:`built-in
sessioning support <../narr/sessions>`. In our ``__init__.py`` we first import
the kind of sessioning we want:
.. literalinclude:: quick_tour/package/hello_world/__init__.py
:language: python
:linenos:
:lineno-start: 2
:lines: 2-3
:emphasize-lines: 2
.. warning::
As noted in the session docs, this example implementation is not intended
for use in settings with security implications.
Now make a "factory" and pass it to the :term:`configurator`'s
``session_factory`` argument:
.. literalinclude:: quick_tour/package/hello_world/__init__.py
:language: python
:linenos:
:lineno-start: 13
:lines: 13-17
:emphasize-lines: 3-5
Pyramid's :term:`request` object now has a ``session`` attribute that we can
use in our view code in ``views.py``:
.. literalinclude:: quick_tour/package/hello_world/views.py
:language: python
:linenos:
:lineno-start: 9
:lines: 9-15
:emphasize-lines: 3-7
We need to update our Jinja2 template to show counter increment in the session:
.. literalinclude:: quick_tour/package/hello_world/templates/mytemplate.jinja2
:language: jinja
:linenos:
:lineno-start: 40
:lines: 40-42
:emphasize-lines: 3
.. seealso:: See also:
:ref:`Quick Tutorial Sessions `, :ref:`sessions_chapter`,
:ref:`flash_messages`, :ref:`session_module`, and
:term:`pyramid_redis_sessions`.
Databases
=========
Web applications mean data. Data means databases. Frequently SQL
databases. SQL databases frequently mean an "ORM"
(object-relational mapper.) In Python, ORM usually leads to the
mega-quality *SQLAlchemy*, a Python package that greatly eases working
with databases.
Pyramid and SQLAlchemy are great friends. That friendship includes a
scaffold!
.. code-block:: bash
$ pcreate --scaffold alchemy sqla_demo
$ cd sqla_demo
$ python setup.py develop
We now have a working sample SQLAlchemy application with all
dependencies installed. The sample project provides a console script to
initialize a SQLite database with tables. Let's run it and then start
the application:
.. code-block:: bash
$ initialize_sqla_demo_db development.ini
$ pserve development.ini
The ORM eases the mapping of database structures into a programming
language. SQLAlchemy uses "models" for this mapping. The scaffold
generated a sample model:
.. literalinclude:: quick_tour/sqla_demo/sqla_demo/models.py
:start-after: Start Sphinx Include
:end-before: End Sphinx Include
View code, which mediates the logic between web requests and the rest
of the system, can then easily get at the data thanks to SQLAlchemy:
.. literalinclude:: quick_tour/sqla_demo/sqla_demo/views.py
:start-after: Start Sphinx Include
:end-before: End Sphinx Include
.. seealso:: See also:
:ref:`Quick Tutorial Databases `,
`SQLAlchemy `_,
:ref:`making_a_console_script`,
:ref:`bfg_sql_wiki_tutorial`, and
:ref:`Application Transactions With pyramid_tm `
Forms
=====
Developers have lots of opinions about web forms, and thus there are many
form libraries for Python. Pyramid doesn't directly bundle a form
library, but *Deform* is a popular choice for forms,
along with its related *Colander* schema system.
As an example, imagine we want a form that edits a wiki page. The form
should have two fields on it, one of them a required title and the
other a rich text editor for the body. With Deform we can express this
as a Colander schema:
.. code-block:: python
class WikiPage(colander.MappingSchema):
title = colander.SchemaNode(colander.String())
body = colander.SchemaNode(
colander.String(),
widget=deform.widget.RichTextWidget()
)
With this in place, we can render the HTML for a form,
perhaps with form data from an existing page:
.. code-block:: python
form = self.wiki_form.render()
We'd like to handle form submission, validation, and saving:
.. code-block:: python
# Get the form data that was posted
controls = self.request.POST.items()
try:
# Validate and either raise a validation error
# or return deserialized data from widgets
appstruct = wiki_form.validate(controls)
except deform.ValidationFailure as e:
# Bail out and render form with errors
return dict(title=title, page=page, form=e.render())
# Change the content and redirect to the view
page['title'] = appstruct['title']
page['body'] = appstruct['body']
Deform and Colander provide a very flexible combination for forms,
widgets, schemas, and validation. Recent versions of Deform also
include a :ref:`retail mode ` for gaining Deform
features on custom forms.
Also the ``deform_bootstrap`` Pyramid add-on restyles the stock Deform
widgets using attractive CSS from Twitter Bootstrap and more powerful widgets
from Chosen.
.. seealso:: See also:
:ref:`Quick Tutorial Forms `,
:ref:`Deform `,
:ref:`Colander `, and
`deform_bootstrap `_
Conclusion
==========
This *Quick Tour* covered a little about a lot. We introduced a long list
of concepts in Pyramid, many of which are expanded on more fully in the
Pyramid developer docs.