:app:`Pyramid` ProjectCreating a
As we saw in :ref:`firstapp_chapter`, it's possible to create a :app:`Pyramid` application completely manually. However, it's usually more convenient to use a :term:`scaffold` to generate a basic :app:`Pyramid` :term:`project`.
A project is a directory that contains at least one Python :term:`package`. You'll use a scaffold to create a project, and you'll create your application logic within a package that lives inside the project. Even if your application is extremely simple, it is useful to place code that drives the application within a package, because: 1) a package is more easily extended with new code and 2) an application that lives inside a package can also be distributed more easily than one which does not live within a package.
:app:`Pyramid` comes with a variety of scaffolds that you can use to generate a project. Each scaffold makes different configuration assumptions about what type of application you're trying to construct.
These scaffolds are rendered using the :term:`PasteDeploy`
The convenience scaffolds included with :app:`Pyramid` differ from each other on a number of axes:
- the persistence mechanism they offer (no persistence mechanism, :term:`ZODB`, or :term:`SQLAlchemy`).
- the mechanism they use to map URLs to code (:term:`traversal` or :term:`URL dispatch`).
- whether or not the
pyramid_beakerlibrary is relied upon as the sessioning implementation (as opposed to no sessioning or default sessioning).
The included scaffolds are these:
- URL mapping via :term:`traversal` and no persistence mechanism.
- URL mapping via :term:`traversal` and persistence via :term:`ZODB`.
- URL mapping via :term:`URL dispatch` and persistence via :term:`SQLAlchemy`
- URL mapping via :term:`traversal` and persistence via :term:`SQLAlchemy`
At this time, each of these scaffolds uses the :term:`Chameleon`
templating system, which is incompatible with Jython. To use scaffolds to
build applications which will run on Jython, you can try the
pyramid_jinja2_starter scaffold which ships as part of the
:term:`pyramid_jinja2` package. You can also just use any above scaffold
and replace the Chameleon template it includes with a :term:`Mako`
Rather than use any of the above scaffolds, Pylons 1 users may feel more
comfortable installing the :term:`Akhet` development environment, which
provides a scaffold named
akhet. This scaffold configures a Pyramid
application in a "Pylons-esque" way, including the use of a :term:`view
handler` to map URLs to code (a handler is much like a Pylons "controller").
Creating the Project
In :ref:`installing_chapter`, you created a virtual Python environment via
virtualenv command. To start a :app:`Pyramid` :term:`project`, use
paster facility installed within the virtualenv. In
:ref:`installing_chapter` we called the virtualenv directory
following command assumes that our current working directory is that
directory. We'll choose the
pyramid_starter scaffold for this purpose.
$ bin/paster create -t pyramid_starter
Or on Windows:
$ Scripts\paster.exe create -t pyramid_starter
The above command uses the
paster create command to create a project with
pyramid_starter scaffold. To use a different scaffold, such as
pyramid_routesalchemy, you'd just change the last argument. For example,
$ bin/paster create -t pyramid_routesalchemy
Or on Windows:
$ Scripts\paster.exe create -t pyramid_routesalchemy
paster create will ask you a single question: the name of the project.
You should use a string without spaces and with only letters in it. Here's
sample output from a run of
paster create on UNIX for a project we name
$ bin/paster create -t pyramid_starter Selected and implied templates: pyramid#pyramid_starter pyramid starter project Enter project name: MyProject Variables: egg: MyProject package: myproject project: MyProject Creating template pyramid Creating directory ./MyProject # ... more output ... Running /Users/chrism/projects/pyramid/bin/python setup.py egg_info
You can skip the interrogative question about a project
paster create by adding the project name to the
command line, e.g.
paster create -t pyramid_starter MyProject.
You may encounter an error when using
paster create if a
dependent Python package is not installed. This will result in a traceback
pkg_resources.DistributionNotFound: <package name>. Simply
Script\easy_install.exe on Windows), with
the missing package name from the error message to work around this issue.
As a result of invoking the
paster create command, a project is created
in a directory named
MyProject. That directory is a :term:`project`
setup.py file in that directory can be used to distribute
your application, or install your application for deployment or development.
.ini file named
development.ini will be created
in the project directory. You will use this
.ini file to configure a
server, to run your application, and to debug your application. It sports
configuration that enables an interactive debugger and settings optimized for
.ini file named
production.ini will also
be created in the project directory. It sports configuration that disables
any interactive debugger (to prevent inappropriate access and disclosure),
and turns off a number of debugging settings. You can use this file to put
your application into production.
MyProject project directory contains an additional subdirectory named
myproject (note the case difference) representing a Python
:term:`package` which holds very simple :app:`Pyramid` sample code. This is
where you'll edit your application's Python code and templates.
Installing your Newly Created Project for Development
To install a newly created project for development, you should
cd to the
newly created project directory and use the Python interpreter from the
:term:`virtualenv` you created during :ref:`installing_chapter` to invoke the
python setup.py develop
The file named
setup.py will be in the root of the paster-generated
project directory. The
python you're invoking should be the one that
lives in the
Scripts on Windows) directory of your virtual
Python environment. Your terminal's current working directory must be the
newly created project directory.
$ cd MyProject $ ../bin/python setup.py develop
Or on Windows:
$ cd MyProject $ ..\Scripts\python.exe setup.py develop
Elided output from a run of this command on UNIX is shown below:
$ cd MyProject $ ../bin/python setup.py develop ... Finished processing dependencies for MyProject==0.0
This will install a :term:`distribution` representing your project into the
interpreter's library set so it can be found by
import statements and by
:term:`PasteDeploy` commands such as
paster proutes and
Running The Tests For Your Application
To run unit tests for your application, you should invoke them using the
Python interpreter from the :term:`virtualenv` you created during
python command that lives in the
directory of your virtualenv).
$ ../bin/python setup.py test -q
Or on Windows:
$ ..\Scripts\python.exe setup.py test -q
Here's sample output from a test run on UNIX:
$ ../bin/python setup.py test -q running test running egg_info writing requirements to MyProject.egg-info/requires.txt writing MyProject.egg-info/PKG-INFO writing top-level names to MyProject.egg-info/top_level.txt writing dependency_links to MyProject.egg-info/dependency_links.txt writing entry points to MyProject.egg-info/entry_points.txt reading manifest file 'MyProject.egg-info/SOURCES.txt' writing manifest file 'MyProject.egg-info/SOURCES.txt' running build_ext .. ---------------------------------------------------------------------- Ran 1 test in 0.108s OK
-q option is passed to the
setup.py test command to limit the
output to a stream of dots. If you don't pass
-q, you'll see more
verbose test result output (which normally isn't very useful).
The tests themselves are found in the
tests.py module in your
create -generated project. Within a project generated by the
pyramid_starter scaffold, a single sample test exists.
Running The Project Application
Once a project is installed for development, you can run the application it
represents using the
paster serve command against the generated
configuration file. In our case, this file is named
$ ../bin/paster serve development.ini
$ ..\Scripts\paster.exe serve development.ini
Here's sample output from a run of
paster serve on UNIX:
$ ../bin/paster serve development.ini Starting server in PID 16601. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543
By default, :app:`Pyramid` applications generated from a scaffold
will listen on TCP port 6543. You can shut down a server started this way by
During development, it's often useful to run
paster serve using its
--reload option. When
--reload is passed to
changes to any Python module your project uses will cause the server to
restart. This typically makes development easier, as changes to Python code
made within a :app:`Pyramid` application is not put into effect until the
For example, on UNIX:
$ ../bin/paster serve development.ini --reload Starting subprocess with file monitor Starting server in PID 16601. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543
For more detailed information about the startup process, see :ref:`startup_chapter`. For more information about environment variables and configuration file settings that influence startup and runtime behavior, see :ref:`environment_chapter`.
Viewing the Application
Once your application is running via
paster serve, you may visit
http://localhost:6543/ in your browser. You will see something in your
browser like what is displayed in the following image:
This is the page shown by default when you visit an unmodified
pyramid_starter application in a browser.
The Debug Toolbar
If you click on the image shown at the right hand top of the page ("^DT"),
you'll be presented with a debug toolbar that provides various niceties while
you're developing. This image will float above every HTML page served by
:app:`Pyramid` while you develop an application, and allows you show the
toolbar as necessary. Click on
Hide to hide the toolbar and show the
For more information about what the debug toolbar allows you to do, see the documentation for pyramid_debugtoolbar.
The debug toolbar will not be shown (and all debugging will be turned off)
when you use the
production.ini file instead of the
ini file to run the application.
You can also turn the debug toolbar off by editing
commenting out the line
pyramid.includes = pyramid_debugtoolbar. For
example, instead of:
Put a hash mark in front of the
Then restart the application to see that the toolbar has been turned off.
The Project Structure
pyramid_starter scaffold generated a :term:`project` (named
MyProject), which contains a Python :term:`package`. The package is
myproject, but it's lowercased; the scaffold
generates a project which contains a package that shares its name except for
paster -generated projects share a similar structure.
MyProject project we've generated has the following directory
MyProject/ |-- CHANGES.txt |-- development.ini |-- MANIFEST.in |-- myproject | |-- __init__.py | |-- resources.py | |-- static | | |-- favicon.ico | | |-- logo.png | | `-- pylons.css | |-- templates | | `-- mytemplate.pt | |-- tests.py | `-- views.py |-- production.ini |-- README.txt |-- setup.cfg `-- setup.py
MyProject :term:`project` directory is the distribution and
deployment wrapper for your application. It contains both the
:term:`package` representing your application as well as files used to
describe, run, and test your application.
CHANGES.txtdescribes the changes you've made to the application. It is conventionally written in :term:`ReStructuredText` format.
README.txtdescribes the application in general. It is conventionally written in :term:`ReStructuredText` format.
development.iniis a :term:`PasteDeploy` configuration file that can be used to execute your application during development.
production.iniis a :term:`PasteDeploy` configuration file that can be used to execute your application in a production configuration.
setup.cfgis a :term:`setuptools` configuration file used by
MANIFEST.inis a :term:`distutils` "manifest" file, naming which files should be included in a source distribution of the package when
python setup.py sdistis run.
setup.pyis the file you'll use to test and distribute your application. It is a standard :term:`setuptools`
development.ini file is a :term:`PasteDeploy` configuration file.
Its purpose is to specify an application to run when you invoke
serve, as well as the deployment settings provided to that application.
development.ini file looks like so:
This file contains several sections including
[server:main] and several other sections related to logging
[app:main] section represents configuration for your :app:`Pyramid`
use setting is the only setting required to be present
[app:main] section. Its default value,
indicates that our MyProject project contains the application that should be
served. Other settings added to this section are passed as keyword arguments
to the function named
main in our package's
__init__.py module. You
can provide startup-time configuration parameters to your application by
adding more settings to this section.
See :ref:`pastedeploy_entry_points` for more information about the
meaning of the
use = egg:MyProject value in this section.
pyramid.reload_templates setting in the
[app:main] section is a
:app:`Pyramid` -specific setting which is passed into the framework. If it
exists, and its value is
true, :term:`Chameleon` and :term:`Mako`
template changes will not require an application restart to be detected. See
:ref:`reload_templates_section` for more information.
pyramid.debug_templates setting in the
[app:main] section is a
:app:`Pyramid` -specific setting which is passed into the framework. If it
exists, and its value is
true, :term:`Chameleon` template exceptions will
contain more detailed and helpful information about the error than when this
false. See :ref:`debug_templates_section` for more information.
options should be turned off for production applications, as template
rendering is slowed when either is turned on.
pyramid.includes setting in the
[app:main] section tells Pyramid
to "include" configuration from another package. In this case, the line
pyramid.includes = pyramid_debugtoolbar tells Pyramid to include
configuration from the
pyramid_debugtoolbar package. This turns on a
debugging panel in development mode which will be shown on the right hand
side of the screen. Including the debug toolbar will also make it possible
to interactively debug exceptions when an error occurs.
Various other settings may exist in this section having to do with debugging or influencing runtime behavior of a :app:`Pyramid` application. See :ref:`environment_chapter` for more information about these settings.
[app:main] signifies that this is the default
application run by
paster serve when it is invoked against this
configuration file. The name
main is a convention used by PasteDeploy
signifying that it is the default application.
[server:main] section of the configuration file configures a WSGI
server which listens on TCP port 6543. It is configured to listen on all
0.0.0.0). This means that any remote system which has TCP
access to your system can see your Pyramid application.
The sections that live between the markers
# Begin logging configuration
# End logging configuration represent Python's standard library
:mod:`logging` module configuration for your application. The sections
between these two markers are passed to the logging module's config file
configuration engine when the
paster serve or
paster pshell commands are executed. The default
configuration sends application logging output to the standard error output
of your terminal. For more information about logging configuration, see
See the :term:`PasteDeploy` documentation for more information about other
types of things you can put into this
.ini file, such as other
applications, :term:`middleware` and alternate :term:`WSGI` server
production.ini file is a :term:`PasteDeploy` configuration file with
a purpose much like that of
development.ini. However, it disables the
debug toolbar, and filters all log messages except those above the WARN
level. It also turns off template development options such that templates
are not automatically reloaded when changed, and turns off all debugging
options. This file is appropriate to use instead of
you put your application into production.
It's important to use
production.ini (and not
benchmark your application and put it into production.
configures your system with a debug toolbar that helps development, but the
inclusion of this toolbar slows down page rendering times by over an order of
magnitude. The debug toolbar is also a potential security risk if you have
it configured incorrectly.
MANIFEST.in file is a :term:`distutils` configuration file which
specifies the non-Python files that should be included when a
:term:`distribution` of your Pyramid project is created when you run
setup.py sdist. Due to the information contained in the default
MANIFEST.in, an sdist of your Pyramid project will include
.rst files, graphics files, and template files, as
.py files. See
more information about the syntax and usage of
Without the presence of a
MANIFEST.in file or without checking your
source code into a version control repository,
setup.py sdist places only
Python source files (files ending with a
.py extension) into tarballs
python setup.py sdist. This means, for example, if your
project was not checked into a setuptools-compatible source control system,
and your project directory didn't contain a
MANIFEST.in file that told
sdist machinery to include
*.pt files, the
myproject/templates/mytemplate.pt file would not be included in the
Projects generated by Pyramid scaffolds include a default
MANIFEST.in file contains declarations which tell it to
include files like
*.js in the generated tarball.
If you include files with extensions other than the files named in the
MANIFEST.in and you don't make use of a setuptools-compatible
version control system, you'll need to edit the
MANIFEST.in file and
include the statements necessary to include your new files. See
http://docs.python.org/distutils/sourcedist.html#principle for more
information about how to do this.
You can also delete
MANIFEST.in from your project and rely on a
setuptools feature which simply causes all files checked into a version
control system to be put into the generated tarball. To allow this to
happen, check all the files that you'd like to be distributed along with your
application's Python files into Subversion. After you do this, when you
setup.py sdist, all files checked into the version control system
will be included in the tarball. If you don't use Subversion, and instead
use a different version control system, you may need to install a setuptools
add-on such as
setuptools-hg for this behavior to
setup.py file is a :term:`setuptools` setup file. It is meant to be
run directly from the command line to perform a variety of functions, such as
testing your application, packaging, and distributing your application.
setup.py is the defacto standard which Python developers use to
distribute their reusable code. You can read more about
and their usage in the Setuptools documentation and The
Hitchhiker's Guide to Packaging.
setup.py looks like this:
setup.py file calls the setuptools
setup function, which does
various things depending on the arguments passed to
setup.py on the
Within the arguments to this function call, information about your application is kept. While it's beyond the scope of this documentation to explain everything about setuptools setup files, we'll provide a whirlwind tour of what exists in this file in this section.
Your application's name can be any string; it is specified in the
field. The version number is specified in the
version value. A short
description is provided in the
description field. The
long_description is conventionally the content of the README and CHANGES
file appended together. The
classifiers field is a list of Trove classifiers
describing your application.
author_email are text fields
which probably don't need any description.
url is a field that should
point at your application project's URL (if any).
packages=find_packages() causes all packages within the project to be
found when packaging the application.
include_package_data will include
non-Python files when the application is packaged if those files are checked
into version control.
zip_safe indicates that this package is not safe
to use as a zipped egg; instead it will always unpack as a directory, which
is more convenient.
tests_require indicate that
this package depends on the
test_suite points at
the package for our application, which means all tests found in the package
will be run when
setup.py test is invoked. We examined
in our discussion of the
development.ini file; this file defines the
main entry point that represents our project's application.
Usually you only need to think about the contents of the
when distributing your application to other people, when adding Python
package dependencies, or when versioning your application for your own use.
For fun, you can try this command now:
$ python setup.py sdist
This will create a tarball of your application in a
MyProject-0.1.tar.gz. You can send this tarball to other people
who want to install and use your application.
setup.cfg file is a :term:`setuptools` configuration file. It
contains various settings related to testing and internationalization:
setup.cfg looks like this:
The values in the default setup file allow various commonly-used internationalization commands and testing commands to work more smoothly.
__init__.pyfile signifies that this is a Python :term:`package`. It also contains code that helps users run the application, including a
mainfunction which is used as a Paste entry point.
resources.pymodule, which contains :term:`resource` code.
templatesdirectory, which contains :term:`Chameleon` (or other types of) templates.
tests.pymodule, which contains unit test code for the application.
views.pymodule, which contains view code for the application.
These are purely conventions established by the scaffold: :app:`Pyramid` doesn't insist that you name things in any particular way. However, it's generally a good idea to follow Pyramid standards for naming, so that other Pyramid developers can get up to speed quickly on your code when you need help.
We need a small Python module that configures our application and which
advertises an entry point for use by our :term:`PasteDeploy`
This is the file named
__init__.py. The presence of an
also informs Python that the directory which contains it is a package.
Line 2 imports the
Rootclass from :mod:`myproject.resources` that we use later.
Within this function, application configuration is performed.
Lines 8-10 register a "default view" (a view that has no
nameattribute). It is registered so that it will be found when the :term:`context` of the request is an instance of the :class:`myproject.resources.Root` class. The first argument to
add_viewpoints at a Python function that does all the work for this view, also known as a :term:`view callable`, via a :term:`dotted Python name`. The view declaration also names a
renderer, which in this case is a template that will be used to render the result of the view callable. This particular view declaration points at
myproject:templates/mytemplate.pt, which is a :term:`asset specification` that specifies the
mytemplate.ptfile within the
templatesdirectory of the
myprojectpackage. The template file it actually points to is a :term:`Chameleon` ZPT template file.
Line 11 registers a static view, which will serve up the files from the
mypackage:static:term:`asset specification` (the
staticdirectory of the
Line 12 returns a :term:`WSGI` application to the caller of the function (Paste).
Much of the heavy lifting in a :app:`Pyramid` application is done by view callables. A :term:`view callable` is the main tool of a :app:`Pyramid` web application developer; it is a bit of code which accepts a :term:`request` and which returns a :term:`response`.
This bit of code was registered as the view callable within
add_view said that the default URL for instances
that are of the class :class:`myproject.resources.Root` should run this
This view callable function is handed a single piece of information: the
:term:`request`. The request is an instance of the :term:`WebOb`
Request class representing the browser's request to our server.
This view returns a dictionary. When this view is invoked, a
:term:`renderer` converts the dictionary returned by the view into HTML, and
returns the result as the :term:`response`. This view is configured to
invoke a renderer which uses a :term:`Chameleon` ZPT template
mypackage:templates/my_template.pt, as specified in the
file call to
See :ref:`views_which_use_a_renderer` for more information about how views, renderers, and templates relate and cooperate.
development.ini has a
true directive indicating that templates should be reloaded when
they change, you won't need to restart the application server to
see changes you make to templates. During development, this is
handy. If this directive had been
false (or if the directive
did not exist), you would need to restart the application server
for each template change. For production applications, you should
set your project's
false to increase
the speed at which templates may be rendered.
resources.py module provides the :term:`resource` data and behavior
for our application. Resources are objects which exist to provide site
structure in applications which use :term:`traversal` to map URLs to code.
We write a class named
Root that provides the behavior for the root
- Lines 1-3 define the Root class. The Root class is a "root resource factory" function that will be called by the :app:`Pyramid` Router for each request when it wants to find the root of the resource tree.
In a "real" application, the Root object would likely not be such a simple object. Instead, it might be an object that could access some persistent data store, such as a database. :app:`Pyramid` doesn't make any assumption about which sort of data storage you'll want to use, so the sample application uses an instance of :class:`myproject.resources.Root` to represent the root.
This directory contains static assets which support the
template. It includes CSS and images.
The single :term:`Chameleon` template that exists in the project. Its contents
are too long to show here, but it displays a default page when rendered. It
is referenced by the call to
add_view as the
renderer attribute in
__init__ file. See :ref:`views_which_use_a_renderer` for more
information about renderers.
tests.py module includes unit tests for your application.
tests.py file has a single unit test defined within it. This
test is executed when you run
python setup.py test. You may add more
tests here as you build your application. You are not required to write
tests to use :app:`Pyramid`, this file is simply provided as convenience and
Modifying Package Structure
It is best practice for your application's code layout to not stray too much from accepted Pyramid scaffold defaults. If you refrain from changing things very much, other Pyramid coders will be able to more quickly understand your application. However, the code layout choices made for you by a scaffold are in no way magical or required. Despite the choices made for you by any scaffold, you can decide to lay your code out any way you see fit.
For example, the configuration method named
:meth:`~pyramid.config.Configurator.add_view` requires you to pass a
:term:`dotted Python name` or a direct object reference as the class or
function to be used as a view. By default, the
would have you add view functions to the
views.py module in your
package. However, you might be more comfortable creating a
directory, and adding a single file for each view.
If your project package name was
myproject and you wanted to arrange all
your views in a Python subpackage within the
views instead of within a single
views.py file, you might:
- Create a
viewsdirectory inside your
mypackagepackage directory (the same directory which holds
- Move the existing
views.pyfile to a file inside the new
viewsdirectory named, say,
- Create a file within the new
__init__.py(it can be empty, this just tells Python that the
viewsdirectory is a package.
Then change the __init__.py of your myproject project (not the
__init__.py you just created in the
views directory, the one in its
parent directory). For example, from something like:
You can then continue to add files to the
views directory, and refer to
view classes or functions within those files via the dotted name passed as
the first argument to
add_view. For example, if you added a file named
anothermodule.py to the
views subdirectory, and added a view callable
my_view to it:
This pattern can be used to rearrage code referred to by any Pyramid API argument which accepts a :term:`dotted Python name` or direct object reference.
Using the Interactive Shell
It is possible to use a Python interpreter prompt loaded with a similar
configuration as would be loaded if you were running your Pyramid application
paster serve. This can be a useful debugging tool. See
:ref:`interactive_shell` for more details.
Using an Alternate WSGI Server
The code generated by a :app:`Pyramid` scaffold assumes that you will be
paster serve command to start your application while you do
paster serve is by no means the only way to start
up and serve a :app:`Pyramid` application. As we saw in
paster serve needn't be invoked at all to run a
:app:`Pyramid` application. The use of
paster serve to run a
:app:`Pyramid` application is purely conventional based on the output of its
Any :term:`WSGI` server is capable of running a :app:`Pyramid` application.
Some WSGI servers don't require the :term:`PasteDeploy` framework's
serve command to do server process management at all. Each :term:`WSGI`
server has its own documentation about how it creates a process to run an
application, and there are many of them, so we cannot provide the details for
each here. But the concepts are largely the same, whatever server you happen
One popular production alternative to a
paster-invoked server is
:term:`mod_wsgi`. You can also use :term:`mod_wsgi` to serve your
:app:`Pyramid` application using the Apache web server rather than any
"pure-Python" server that is started as a result of
paster serve. See
:ref:`modwsgi_tutorial` for details. However, it is usually easier to
develop an application using a
paster serve -invoked webserver, as
exception and debugging output will be sent to the console.