Defining Views¶
A view callable in a Pyramid application is typically a simple Python function that accepts a single parameter named request. A view callable is assumed to return a response object.
The request object has a dictionary as an attribute named matchdict
. A
matchdict
maps the placeholders in the matching URL pattern
to the
substrings of the path in the request URL. For instance, if a call to
pyramid.config.Configurator.add_route()
has the pattern /{one}/{two}
,
and a user visits http://example.com/foo/bar
, our pattern would be matched
against /foo/bar
and the matchdict
would look like {'one':'foo',
'two':'bar'}
.
Declaring Dependencies in Our setup.py
File¶
The view code in our application will depend on a package which is not a
dependency of the original "tutorial" application. The original "tutorial"
application was generated by the pcreate
command; it doesn't know
about our custom application requirements.
We need to add a dependency on the docutils
package to our tutorial
package's setup.py
file by assigning this dependency to the requires
parameter in the setup()
function.
Open tutorial/setup.py
and edit it to look like the following:
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 44 45 46 47 48 | import os
from setuptools import setup, find_packages
here = os.path.abspath(os.path.dirname(__file__))
with open(os.path.join(here, 'README.txt')) as f:
README = f.read()
with open(os.path.join(here, 'CHANGES.txt')) as f:
CHANGES = f.read()
requires = [
'pyramid',
'pyramid_chameleon',
'pyramid_debugtoolbar',
'pyramid_tm',
'SQLAlchemy',
'transaction',
'zope.sqlalchemy',
'waitress',
'docutils',
]
setup(name='tutorial',
version='0.0',
description='tutorial',
long_description=README + '\n\n' + CHANGES,
classifiers=[
"Programming Language :: Python",
"Framework :: Pyramid",
"Topic :: Internet :: WWW/HTTP",
"Topic :: Internet :: WWW/HTTP :: WSGI :: Application",
],
author='',
author_email='',
url='',
keywords='web wsgi bfg pylons pyramid',
packages=find_packages(),
include_package_data=True,
zip_safe=False,
test_suite='tutorial',
install_requires=requires,
entry_points="""\
[paste.app_factory]
main = tutorial:main
[console_scripts]
initialize_tutorial_db = tutorial.scripts.initializedb:main
""",
)
|
Only the highlighted line needs to be added.
Running setup.py develop
¶
Since a new software dependency was added, you will need to run python
setup.py develop
again inside the root of the tutorial
package to obtain
and register the newly added dependency distribution.
Make sure your current working directory is the root of the project (the
directory in which setup.py
lives) and execute the following command.
On UNIX:
$ cd tutorial
$ $VENV/bin/python setup.py develop
On Windows:
c:\pyramidtut> cd tutorial
c:\pyramidtut\tutorial> %VENV%\Scripts\python setup.py develop
Success executing this command will end with a line to the console something like:
Finished processing dependencies for tutorial==0.0
Adding view functions in views.py
¶
It's time for a major change. Open tutorial/tutorial/views.py
and edit it
to look like the following:
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 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 | import cgi
import re
from docutils.core import publish_parts
from pyramid.httpexceptions import (
HTTPFound,
HTTPNotFound,
)
from pyramid.view import view_config
from .models import (
DBSession,
Page,
)
# regular expression used to find WikiWords
wikiwords = re.compile(r"\b([A-Z]\w+[A-Z]+\w+)")
@view_config(route_name='view_wiki')
def view_wiki(request):
return HTTPFound(location = request.route_url('view_page',
pagename='FrontPage'))
@view_config(route_name='view_page', renderer='templates/view.pt')
def view_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).first()
if page is None:
return HTTPNotFound('No such page')
def check(match):
word = match.group(1)
exists = DBSession.query(Page).filter_by(name=word).all()
if exists:
view_url = request.route_url('view_page', pagename=word)
return '<a href="%s">%s</a>' % (view_url, cgi.escape(word))
else:
add_url = request.route_url('add_page', pagename=word)
return '<a href="%s">%s</a>' % (add_url, cgi.escape(word))
content = publish_parts(page.data, writer_name='html')['html_body']
content = wikiwords.sub(check, content)
edit_url = request.route_url('edit_page', pagename=pagename)
return dict(page=page, content=content, edit_url=edit_url)
@view_config(route_name='add_page', renderer='templates/edit.pt')
def add_page(request):
pagename = request.matchdict['pagename']
if 'form.submitted' in request.params:
body = request.params['body']
page = Page(name=pagename, data=body)
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
save_url = request.route_url('add_page', pagename=pagename)
page = Page(name='', data='')
return dict(page=page, save_url=save_url)
@view_config(route_name='edit_page', renderer='templates/edit.pt')
def edit_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).one()
if 'form.submitted' in request.params:
page.data = request.params['body']
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
return dict(
page=page,
save_url = request.route_url('edit_page', pagename=pagename),
)
|
The highlighted lines need to be added or edited.
We added some imports and created a regular expression to find "WikiWords".
We got rid of the my_view
view function and its decorator that was added
when we originally rendered the alchemy
scaffold. It was only an example
and isn't relevant to our application.
Then we added four view callable functions to our views.py
module:
view_wiki()
- Displays the wiki itself. It will answer on the root URL.view_page()
- Displays an individual page.add_page()
- Allows the user to add a page.edit_page()
- Allows the user to edit a page.
We'll describe each one briefly in the following sections.
Note
There is nothing special about the filename views.py
. A project may
have many view callables throughout its codebase in arbitrarily named
files. Files implementing view callables often have view
in their
filenames (or may live in a Python subpackage of your application package
named views
), but this is only by convention.
The view_wiki
view function¶
Following is the code for the view_wiki
view function and its decorator:
20 21 22 23 24 | @view_config(route_name='view_wiki')
def view_wiki(request):
return HTTPFound(location = request.route_url('view_page',
pagename='FrontPage'))
|
view_wiki()
is the default view that gets called when a request is
made to the root URL of our wiki. It always redirects to an URL which
represents the path to our "FrontPage".
The view_wiki
view callable always redirects to the URL of a Page resource
named "FrontPage". To do so, it returns an instance of the
pyramid.httpexceptions.HTTPFound
class (instances of which implement
the pyramid.interfaces.IResponse
interface, like
pyramid.response.Response
does). It uses the
pyramid.request.Request.route_url()
API to construct an URL to the
FrontPage
page (i.e., http://localhost:6543/FrontPage
), and uses it as
the "location" of the HTTPFound
response, forming an HTTP redirect.
The view_page
view function¶
Here is the code for the view_page
view function and its decorator:
25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | @view_config(route_name='view_page', renderer='templates/view.pt')
def view_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).first()
if page is None:
return HTTPNotFound('No such page')
def check(match):
word = match.group(1)
exists = DBSession.query(Page).filter_by(name=word).all()
if exists:
view_url = request.route_url('view_page', pagename=word)
return '<a href="%s">%s</a>' % (view_url, cgi.escape(word))
else:
add_url = request.route_url('add_page', pagename=word)
return '<a href="%s">%s</a>' % (add_url, cgi.escape(word))
content = publish_parts(page.data, writer_name='html')['html_body']
content = wikiwords.sub(check, content)
edit_url = request.route_url('edit_page', pagename=pagename)
return dict(page=page, content=content, edit_url=edit_url)
|
view_page()
is used to display a single page of our wiki. It renders the
reStructuredText body of a page (stored as the data
attribute of a
Page
model object) as HTML. Then it substitutes an HTML anchor for each
WikiWord reference in the rendered HTML using a compiled regular expression.
The curried function named check
is used as the first argument to
wikiwords.sub
, indicating that it should be called to provide a value for
each WikiWord match found in the content. If the wiki already contains a
page with the matched WikiWord name, check()
generates a view
link to be used as the substitution value and returns it. If the wiki does
not already contain a page with the matched WikiWord name, check()
generates an "add" link as the substitution value and returns it.
As a result, the content
variable is now a fully formed bit of HTML
containing various view and add links for WikiWords based on the content of
our current page object.
We then generate an edit URL because it's easier to do here than in the
template, and we return a dictionary with a number of arguments. The fact that
view_page()
returns a dictionary (as opposed to a response object)
is a cue to Pyramid that it should try to use a renderer
associated with the view configuration to render a response. In our case, the
renderer used will be the templates/view.pt
template, as indicated in the
@view_config
decorator that is applied to view_page()
.
The add_page
view function¶
Here is the code for the add_page
view function and its decorator:
47 48 49 50 51 52 53 54 55 56 57 58 | @view_config(route_name='add_page', renderer='templates/edit.pt')
def add_page(request):
pagename = request.matchdict['pagename']
if 'form.submitted' in request.params:
body = request.params['body']
page = Page(name=pagename, data=body)
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
save_url = request.route_url('add_page', pagename=pagename)
page = Page(name='', data='')
return dict(page=page, save_url=save_url)
|
add_page()
is invoked when a user clicks on a WikiWord which
isn't yet represented as a page in the system. The check
function
within the view_page
view generates URLs to this view.
add_page()
also acts as a handler for the form that is generated
when we want to add a page object. The matchdict
attribute of the
request passed to the add_page()
view will have the values we need
to construct URLs and find model objects.
The matchdict
will have a 'pagename'
key that matches the name of
the page we'd like to add. If our add view is invoked via,
e.g., http://localhost:6543/add_page/SomeName
, the value for
'pagename'
in the matchdict
will be 'SomeName'
.
If the view execution is a result of a form submission (i.e., the expression
'form.submitted' in request.params
is True
), we grab the page body
from the form data, create a Page object with this page body and the name
taken from matchdict['pagename']
, and save it into the database using
DBSession.add
. We then redirect back to the view_page
view for the
newly created page.
If the view execution is not a result of a form submission (i.e., the
expression 'form.submitted' in request.params
is False
), the view
callable renders a template. To do so, it generates a save_url
which the
template uses as the form post URL during rendering. We're lazy here, so
we're going to use the same template (templates/edit.pt
) for the add
view as well as the page edit view. To do so we create a dummy Page object
in order to satisfy the edit form's desire to have some page object
exposed as page
. Pyramid will render the template associated
with this view to a response.
The edit_page
view function¶
Here is the code for the edit_page
view function and its decorator:
60 61 62 63 64 65 66 67 68 69 70 71 72 | @view_config(route_name='edit_page', renderer='templates/edit.pt')
def edit_page(request):
pagename = request.matchdict['pagename']
page = DBSession.query(Page).filter_by(name=pagename).one()
if 'form.submitted' in request.params:
page.data = request.params['body']
DBSession.add(page)
return HTTPFound(location = request.route_url('view_page',
pagename=pagename))
return dict(
page=page,
save_url = request.route_url('edit_page', pagename=pagename),
)
|
edit_page()
is invoked when a user clicks the "Edit this
Page" button on the view form. It renders an edit form but it also acts as
the handler for the form it renders. The matchdict
attribute of the
request passed to the edit_page
view will have a 'pagename'
key
matching the name of the page the user wants to edit.
If the view execution is a result of a form submission (i.e., the expression
'form.submitted' in request.params
is True
), the view grabs the
body
element of the request parameters and sets it as the data
attribute of the page object. It then redirects to the view_page
view
of the wiki page.
If the view execution is not a result of a form submission (i.e., the
expression 'form.submitted' in request.params
is False
), the view
simply renders the edit form, passing the page object and a save_url
which will be used as the action of the generated form.
Adding templates¶
The view_page
, add_page
and edit_page
views that we've added
reference a template. Each template is a Chameleon
ZPT template. These templates will live in the templates
directory of our tutorial package. Chameleon templates must have a .pt
extension to be recognized as such.
The view.pt
template¶
Create tutorial/tutorial/templates/view.pt
and add the following
content:
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 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | <!DOCTYPE html>
<html lang="${request.locale_name}">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="pyramid web application">
<meta name="author" content="Pylons Project">
<link rel="shortcut icon" href="${request.static_url('tutorial:static/pyramid-16x16.png')}">
<title>${page.name} - Pyramid tutorial wiki (based on
TurboGears 20-Minute Wiki)</title>
<!-- Bootstrap core CSS -->
<link href="//oss.maxcdn.com/libs/twitter-bootstrap/3.0.3/css/bootstrap.min.css" rel="stylesheet">
<!-- Custom styles for this scaffold -->
<link href="${request.static_url('tutorial:static/theme.css')}" rel="stylesheet">
<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="//oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="//oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->
</head>
<body>
<div class="starter-template">
<div class="container">
<div class="row">
<div class="col-md-2">
<img class="logo img-responsive" src="${request.static_url('tutorial:static/pyramid.png')}" alt="pyramid web framework">
</div>
<div class="col-md-10">
<div class="content">
<div tal:replace="structure content">
Page text goes here.
</div>
<p>
<a tal:attributes="href edit_url" href="">
Edit this page
</a>
</p>
<p>
Viewing <strong><span tal:replace="page.name">
Page Name Goes Here</span></strong>
</p>
<p>You can return to the
<a href="${request.application_url}">FrontPage</a>.
</p>
</div>
</div>
</div>
<div class="row">
<div class="copyright">
Copyright © Pylons Project
</div>
</div>
</div>
</div>
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="//oss.maxcdn.com/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="//oss.maxcdn.com/libs/twitter-bootstrap/3.0.3/js/bootstrap.min.js"></script>
</body>
</html>
|
This template is used by view_page()
for displaying a single
wiki page. It includes:
- A
div
element that is replaced with thecontent
value provided by the view (lines 36-38).content
contains HTML, so thestructure
keyword is used to prevent escaping it (i.e., changing ">" to ">", etc.) - A link that points at the "edit" URL which invokes the
edit_page
view for the page being viewed (lines 40-42).
The edit.pt
template¶
Create tutorial/tutorial/templates/edit.pt
and add the following
content:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | <!DOCTYPE html>
<html lang="${request.locale_name}">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta name="description" content="pyramid web application">
<meta name="author" content="Pylons Project">
<link rel="shortcut icon" href="${request.static_url('tutorial:static/pyramid-16x16.png')}">
<title>${page.name} - Pyramid tutorial wiki (based on
TurboGears 20-Minute Wiki)</title>
<!-- Bootstrap core CSS -->
<link href="//oss.maxcdn.com/libs/twitter-bootstrap/3.0.3/css/bootstrap.min.css" rel="stylesheet">
<!-- Custom styles for this scaffold -->
<link href="${request.static_url('tutorial:static/theme.css')}" rel="stylesheet">
<!-- HTML5 shim and Respond.js IE8 support of HTML5 elements and media queries -->
<!--[if lt IE 9]>
<script src="//oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script src="//oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]-->
</head>
<body>
<div class="starter-template">
<div class="container">
<div class="row">
<div class="col-md-2">
<img class="logo img-responsive" src="${request.static_url('tutorial:static/pyramid.png')}" alt="pyramid web framework">
</div>
<div class="col-md-10">
<div class="content">
<p>
Editing <strong><span tal:replace="page.name">Page Name Goes
Here</span></strong>
</p>
<p>You can return to the
<a href="${request.application_url}">FrontPage</a>.
</p>
<form action="${save_url}" method="post">
<div class="form-group">
<textarea class="form-control" name="body" tal:content="page.data" rows="10" cols="60"></textarea>
</div>
<div class="form-group">
<button type="submit" name="form.submitted" value="Save" class="btn btn-default">Save</button>
</div>
</form>
</div>
</div>
</div>
<div class="row">
<div class="copyright">
Copyright © Pylons Project
</div>
</div>
</div>
</div>
<!-- Bootstrap core JavaScript
================================================== -->
<!-- Placed at the end of the document so the pages load faster -->
<script src="//oss.maxcdn.com/libs/jquery/1.10.2/jquery.min.js"></script>
<script src="//oss.maxcdn.com/libs/twitter-bootstrap/3.0.3/js/bootstrap.min.js"></script>
</body>
</html>
|
This template is used by add_page()
and edit_page()
for adding and
editing a wiki page. It displays a page containing a form that includes:
- A 10 row by 60 column
textarea
field namedbody
that is filled with any existing page data when it is rendered (line 45). - A submit button that has the name
form.submitted
(line 48).
The form POSTs back to the save_url
argument supplied by the view (line
43). The view will use the body
and form.submitted
values.
Note
Our templates use a request
object that none of our tutorial
views return in their dictionary. request
is one of several names that
are available "by default" in a template when a template renderer is used.
See System Values Used During Rendering for information about other names that
are available by default when a template is used as a renderer.
Static Assets¶
Our templates name static assets, including CSS and images. We don't need
to create these files within our package's static
directory because they
were provided at the time we created the project.
As an example, the CSS file will be accessed via
http://localhost:6543/static/theme.css
by virtue of the call to the
add_static_view
directive we've made in the __init__.py
file. Any
number and type of static assets can be placed in this directory (or
subdirectories) and are just referred to by URL or by using the convenience
method static_url
, e.g.,
request.static_url('<package>:static/foo.css')
within templates.
Adding Routes to __init__.py
¶
The __init__.py
file contains
pyramid.config.Configurator.add_route()
calls which serve to add routes
to our application. First, we’ll get rid of the existing route created by
the template using the name 'home'
. It’s only an example and isn’t
relevant to our application.
We then need to add four calls to add_route
. Note that the ordering of
these declarations is very important. route
declarations are matched in
the order they're found in the __init__.py
file.
- Add a declaration which maps the pattern
/
(signifying the root URL) to the route namedview_wiki
. It maps to ourview_wiki
view callable by virtue of the@view_config
attached to theview_wiki
view function indicatingroute_name='view_wiki'
. - Add a declaration which maps the pattern
/{pagename}
to the route namedview_page
. This is the regular view for a page. It maps to ourview_page
view callable by virtue of the@view_config
attached to theview_page
view function indicatingroute_name='view_page'
. - Add a declaration which maps the pattern
/add_page/{pagename}
to the route namedadd_page
. This is the add view for a new page. It maps to ouradd_page
view callable by virtue of the@view_config
attached to theadd_page
view function indicatingroute_name='add_page'
. - Add a declaration which maps the pattern
/{pagename}/edit_page
to the route namededit_page
. This is the edit view for a page. It maps to ouredit_page
view callable by virtue of the@view_config
attached to theedit_page
view function indicatingroute_name='edit_page'
.
As a result of our edits, the __init__.py
file should look
something like:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | from pyramid.config import Configurator
from sqlalchemy import engine_from_config
from .models import (
DBSession,
Base,
)
def main(global_config, **settings):
""" This function returns a Pyramid WSGI application.
"""
engine = engine_from_config(settings, 'sqlalchemy.')
DBSession.configure(bind=engine)
Base.metadata.bind = engine
config = Configurator(settings=settings)
config.include('pyramid_chameleon')
config.add_static_view('static', 'static', cache_max_age=3600)
config.add_route('view_wiki', '/')
config.add_route('view_page', '/{pagename}')
config.add_route('add_page', '/add_page/{pagename}')
config.add_route('edit_page', '/{pagename}/edit_page')
config.scan()
return config.make_wsgi_app()
|
The highlighted lines are the ones that need to be added or edited.
Viewing the application in a browser¶
We can finally examine our application in a browser (See Start the application). Launch a browser and visit each of the following URLs, checking that the result is as expected:
- http://localhost:6543/ invokes the
view_wiki
view. This always redirects to theview_page
view of theFrontPage
page object. - http://localhost:6543/FrontPage invokes the
view_page
view of the front page object. - http://localhost:6543/FrontPage/edit_page invokes the edit view for the front page object.
- http://localhost:6543/add_page/SomePageName invokes the add view for a page.
- To generate an error, visit http://localhost:6543/foobars/edit_page which
will generate a
NoResultFound: No row was found for one()
error. You'll see an interactive traceback facility provided by pyramid_debugtoolbar.