Skip to content
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
1189 lines (870 sloc) 46.9 KB

Creating a :app:`Pyramid` Project

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 our :term:`cookiecutter` to generate a basic :app:`Pyramid` :term:`project`.

A project is a directory that contains at least one Python :term:`package`. You'll use the :app:`Pyramid` cookiecutter 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.

The Pylons Project provides a :app:`Pyramid` cookiecutter that you can use to generate a project. Our cookiecutter allows several configuration options to generate the type of application you're trying to construct.

This cookiecutter is rendered using the cookiecutter command that you may install.

.. seealso::

    See also `Cookiecutter Installation <>`_.

.. index::
   single: cookiecutters
   single: pyramid-cookiecutter-starter

:app:`Pyramid` cookiecutters

The Pyramid cookiecutter released under the Pylons Project offers the following configuration options:

All configuration options offer a choice of templating language.

The configuration of mapping URLs to code (routing) depends on the backend option selected, with additional variations as follows.

:term:`URL dispatch` for routing
SQLite for persistent storage, :term:`SQLAlchemy` for an ORM, :term:`URL dispatch` for routing, and :term:`Alembic` for database migrations
:term:`ZODB` for persistent storage and :term:`traversal` for routing
.. index::
   single: creating a project
   single: project
   single: cookiecutter

Creating the Project

In :ref:`installing_chapter`, you created a virtual Python environment via the venv command. We called the virtual environment directory env and set an environment variable VENV to its path.

We assume that you :ref:`previously installed cookiecutter <cookiecutters>`, following its installation instructions.

When we invoke cookiecutter, it will create a directory that represents our project.

We assume our current working directory is the value of VENV.

On all platforms, generate a project using cookiecutter.

cookiecutter gh:Pylons/pyramid-cookiecutter-starter --checkout master

If prompted for the first item, accept the default yes by hitting return.

You've cloned ~/.cookiecutters/pyramid-cookiecutter-starter before.
Is it okay to delete and re-clone it? [yes]: yes
project_name [Pyramid Scaffold]: myproject
repo_name [myproject]: myproject
Select template_language:
1 - jinja2
2 - chameleon
3 - mako
Choose from 1, 2, 3 [1]: 1
Select backend:
1 - none
2 - sqlalchemy
3 - zodb
Choose from 1, 2, 3 [1]: 1

We then run through the following commands.

On Unix:

# Reset our environment variable for a new virtual environment.
export VENV=~/env/myproject/env
# Change directory into your newly created project.
cd myproject
# Create a new virtual environment...
python3 -m venv $VENV
# ...where we upgrade packaging tools.
env/bin/pip install --upgrade pip setuptools

Or on Windows:

# Reset our environment variable for a new virtual environment.
set VENV=c:\env\myproject\env
# Change directory into your newly created project.
cd myproject
# Create a new virtual environment...
python -m venv %VENV%
# ...where we upgrade packaging tools.
%VENV%\Scripts\pip install --upgrade pip setuptools

As a result of invoking the cookiecutter command, a directory named myproject is created. That directory is a :term:`project` directory. The file in that directory can be used to distribute your application, or install your application for deployment or development.

An .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 contains configuration that enables an interactive debugger and :term:`settings` optimized for development.

Another .ini file named production.ini will also be created in the project directory. It contains 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.

The myproject project directory contains an additional subdirectory named myproject 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.

We created this project in a directory next to its virtual environment directory. However, note that this is not mandatory. The project directory can go more or less anywhere on your filesystem. You don't need to put it in a special "web server" directory. You could put it within a virtual environment directory. The author uses Linux mainly, and tends to put project directories which he creates within his ~/projects directory. On Windows, it's a good idea to put project directories within a directory that contains no space characters, so it's wise to avoid a path that contains, i.e., My Documents. As a result, the author, when he uses Windows, just puts his projects in C:\projects.


You'll need to avoid using cookiecutter to create a project with the same name as a Python standard library component. In particular, this means you should avoid using the names site or test, both of which conflict with Python standard library packages. You should also avoid using the name pyramid, which will conflict with Pyramid itself.

.. index::
   single: develop
   single: development install

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:`virtual environment` you created during :ref:`installing_chapter` to invoke the command pip install -e ., which installs the project in development mode (-e is for "editable") into the current directory (.).

The file named will be in the root of the cookiecutter-generated project directory. The python you're invoking should be the one that lives in the bin (or Scripts on Windows) directory of your virtual Python environment. Your terminal's current working directory must be the newly created project directory.

On Unix:

$VENV/bin/pip install -e .

Or on Windows:

%VENV%\Scripts\pip install -e .

Elided output from a run of this command on Unix is shown below:

Running develop for myproject
Successfully installed Jinja2-2.8 Mako-1.0.6 MarkupSafe-0.23 \
PasteDeploy-1.5.2 Pygments-2.1.3 WebOb-1.7.0 myproject pyramid-1.7.3 \
pyramid-debugtoolbar-3.0.5 pyramid-jinja2-2.7 pyramid-mako-1.0.2 \
repoze.lru-0.6 translationstring-1.3 venusian-1.0 waitress-1.0.1 \
zope.deprecation-4.2.0 zope.interface-4.3.3

This will install a :term:`distribution` representing your project into the virtual environment interpreter's library set so it can be found by import statements and by other console scripts such as pserve, pshell, proutes, and pviews.

.. index::
   single: running tests
   single: tests (running)

Running the Tests for Your Application

To run unit tests for your application, you must first install the testing dependencies.

On Unix:

$VENV/bin/pip install -e ".[testing]"

On Windows:

%VENV%\Scripts\pip install -e ".[testing]"

Once the testing requirements are installed, then you can run the tests using the pytest command that was just installed in the bin directory of your virtual environment.

On Unix:

$VENV/bin/pytest -q

On Windows:

%VENV%\Scripts\pytest -q

Here's sample output from a test run on Unix:

$VENV/bin/pytest -q
2 passed in 0.47 seconds

The tests themselves are found in the module in your cookiecutter-generated project. Within a project generated by the pyramid-cookiecutter-starter cookiecutter, only two sample tests exist.


The -q option is passed to the pytest command to limit the output to a stream of dots. If you don't pass -q, you'll see verbose test result output (which normally isn't very useful).

Alternatively, if you'd like to see test coverage, pass the --cov option to pytest:

$VENV/bin/pytest --cov -q

Cookiecutters include configuration defaults for pytest and test coverage. These configuration files are pytest.ini and .coveragerc, located at the root of your package. Without these defaults, we would need to specify the path to the module on which we want to run tests and coverage.

$VENV/bin/pytest --cov=myproject myproject/ -q
.. seealso:: See ``pytest``'s documentation for :ref:`pytest:usage` or invoke
   ``pytest -h`` to see its full set of options.

.. index::
   single: running an application
   single: pserve
   single: reload
   single: starting

Running the Project Application

.. seealso:: See also the output of :ref:`pserve --help <pserve_script>`.

Once a project is installed for development, you can run the application it represents using the pserve command against the generated configuration file. In our case, this file is named development.ini.

On Unix:

$VENV/bin/pserve development.ini

On Windows:

%VENV%\Scripts\pserve development.ini

Here's sample output from a run of pserve on Unix:

$VENV/bin/pserve development.ini
Starting server in PID 77171.
Serving on http://localhost:6543
Serving on http://localhost:6543

Access is restricted such that only a browser running on the same machine as Pyramid will be able to access your Pyramid application. However, if you want to open access to other machines on the same network, then edit the development.ini file, and replace the listen value in the [server:main] section, changing it from localhost:6543 to *:6543 (this is equivalent to [::]:6543). For example:

use = egg:waitress#main
listen = *:6543

Now when you use pserve to start the application, it will respond to requests on all IP addresses possessed by your system, not just requests to localhost. This is what the in serving on means. The server will respond to requests made to and on any external IP address. For example, your system might be configured to have an external IP address If that's the case, if you use a browser running on the same system as Pyramid, it will be able to access the application via as well as via However, other people on other computers on the same network will also be able to visit your Pyramid application in their browser by visiting The same holds true if you use IPv6. [::] means the same as but for IPv6 protocol.

You can change the port on which the server runs on by changing the same portion of the development.ini file. For example, you can change the listen = localhost:6543 line in the development.ini file's [server:main] section to listen = localhost:8080 to run the server on port 8080 instead of port 6543.

You can shut down a server started this way by pressing Ctrl-C (or Ctrl-Break on Windows).

The default server used to run your Pyramid application when a project is created from a cookiecutter is named :term:`Waitress`. This server is what prints the Serving on... line when you run pserve. It's a good idea to use this server during development because it's very simple. It can also be used for light production. Setting your application up under a different server is not advised until you've done some development work under the default server, particularly if you're not yet experienced with Python web development. Python web server setup can be complex, and you should get some confidence that your application works in a default environment before trying to optimize it or make it "more like production". It's awfully easy to get sidetracked trying to set up a non-default server for hours without actually starting to do any development. One of the nice things about Python web servers is that they're largely interchangeable, so if your application works under the default server, it will almost certainly work under any other server in production if you eventually choose to use a different one. Don't worry about it right now.

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`.

Reloading Code

During development, it's often useful to run pserve using its --reload option. When --reload is passed to pserve, 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 server restarts.

For example, on Unix:

$VENV/bin/pserve development.ini --reload
Starting subprocess with file monitor
Starting server in PID 16601.
Serving on http://localhost:6543
Serving on http://localhost:6543

Now if you make a change to any of your project's .py files or .ini files, you'll see the server restart automatically:

development.ini changed; reloading...
-------------------- Restarting --------------------
Starting server in PID 16602.
Serving on http://localhost:6543
Serving on http://localhost:6543

Changes to template files (such as .pt or .mak files) won't cause the server to restart. Changes to template files don't require a server restart as long as the pyramid.reload_templates setting in the development.ini file is true. Changes made to template files when this setting is true will take effect immediately without a server restart.

.. index::
   single: WSGI

Viewing the Application

Once your application is running via pserve, 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 cookiecutter generated pyramid-cookiecutter-starter application in a browser.

.. index::
   single: debug toolbar

The Debug Toolbar


If you click on the :app:`Pyramid` logo at the top right of the page, a new target window will open to present a debug toolbar that provides various niceties while you're developing. This logo will float above every HTML page served by :app:`Pyramid` while you develop an application, and allows you to show the toolbar as necessary.


If you don't see the Pyramid logo on the top right of the page, it means you're browsing from a system that does not have debugging access. By default, for security reasons, only a browser originating from localhost ( can see the debug toolbar. To allow your browser on a remote system to access the server, add a line within the [app:main] section of the development.ini file in the form debugtoolbar.hosts = X .X.X.X. For example, if your Pyramid application is running on a remote system, and you're browsing from a host with the IP address, you'd add something like this to enable the toolbar when your system contacts Pyramid:

# .. other settings ...
debugtoolbar.hosts =

For more information about what the debug toolbar allows you to do, see the :ref:`documentation for pyramid_debugtoolbar <toolbar:overview>`.

The debug toolbar will not be shown (and all debugging will be turned off) when you use the production.ini file instead of the development.ini ini file to run the application.

You can also turn the debug toolbar off by editing development.ini and commenting out a line. For example, instead of:

Put a hash mark at the beginning of the pyramid_debugtoolbar line:

Then restart the application to see that the toolbar has been turned off.

Note that if you comment out the pyramid_debugtoolbar line, the # must be in the first column. If you put it anywhere else, and then attempt to restart the application, you'll receive an error that ends something like this:

ImportError: No module named #pyramid_debugtoolbar
.. index::
   single: project structure

The Project Structure

The pyramid-cookiecutter-starter cookiecutter generated a :term:`project` (named myproject), which contains a Python :term:`package`. The package is also named myproject; the cookiecutter generates a project which contains a package that shares its name.

All :app:`Pyramid` cookiecutter-generated projects share a similar structure. The myproject project we've generated has the following directory structure:

├── .coveragerc
├── .gitignore
├── CHANGES.txt
├── myproject
│   ├──
│   ├──
│   ├── static
│   │   ├── pyramid-16x16.png
│   │   ├── pyramid.png
│   │   └── theme.css
│   ├── templates
│   │   ├── 404.jinja2
│   │   ├── layout.jinja2
│   │   └── mytemplate.jinja2
│   ├──
│   └── views
│       ├──
│       ├──
│       └──
├── README.txt
├── development.ini
├── production.ini
├── pytest.ini

The myproject :term:`Project`

The myproject :term:`project` directory is the distribution and deployment wrapper for your application. It contains both the myproject :term:`package` representing your application as well as files used to describe, run, and test your application.

  1. .coveragerc configures coverage when running tests.
  2. .gitignore tells git which files and directories to ignore from source code version control.
  3. CHANGES.txt describes the changes you've made to the application. It is conventionally written in :term:`reStructuredText` format.
  4. is a :term:`distutils` "manifest" file, naming which files should be included in a source distribution of the package when python sdist is run.
  5. README.txt describes the application in general. It is conventionally written in :term:`reStructuredText` format.
  6. development.ini is a :term:`PasteDeploy` configuration file that can be used to execute your application during development.
  7. production.ini is a :term:`PasteDeploy` configuration file that can be used to execute your application in a production configuration.
  8. pytest.ini is a configuration file for running tests.
  9. is the file you'll use to test and distribute your application. It is a standard :term:`Setuptools` file.
.. index::
   single: PasteDeploy
   single: ini file


The development.ini file is a :term:`PasteDeploy` configuration file. Its purpose is to specify an application to run when you invoke pserve, as well as the deployment settings provided to that application.

The generated development.ini file looks like so:

.. literalinclude:: myproject/development.ini
   :language: ini

This file contains several sections including [app:main], [server:main], and several other sections related to logging configuration.

The [app:main] section represents configuration for your :app:`Pyramid` application. The use setting is the only setting required to be present in the [app:main] section. Its default value, egg:myproject, 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 module. You can provide startup-time configuration parameters to your application by adding more settings to this section.

.. seealso:: See :ref:`pastedeploy_entry_points` for more information about the
   meaning of the ``use = egg:myproject`` value in this section.

The 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, supported template changes will not require an application restart to be detected. See :ref:`reload_templates_section` for more information.


The pyramid.reload_templates option should be turned off for production applications, as template rendering is slowed when it is turned on.

The 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 can be opened by clicking on the :app:`Pyramid` logo on the top right 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.

The name main in [app:main] signifies that this is the default application run by pserve when it is invoked against this configuration file. The name main is a convention used by PasteDeploy signifying that it is the default application.

The [server:main] section of the configuration file configures a WSGI server which listens on TCP port 6543. It is configured to listen on localhost only (

The sections after # logging configuration represent Python's standard library :mod:`logging` module configuration for your application. The default configuration sends application logging output to the standard error output of your terminal. For more information see :ref:`logging_chapter`.

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 implementations.

.. index::
   single: production.ini


The 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 development.ini when you put your application into production.

It's important to use production.ini (and not development.ini) to benchmark your application and put it into production. development.ini 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.

.. index::

The 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 python sdist. Due to the information contained in the default, an sdist of your Pyramid project will include .txt files, .ini files, .rst files, graphics files, and template files, as well as .py files. See for more information about the syntax and usage of

Without the presence of a file or without checking your source code into a version control repository, sdist places only Python source files (files ending with a .py extension) into tarballs generated by python 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 file that told the sdist machinery to include *.pt files, the myproject/templates/ file would not be included in the generated tarball.

Projects generated by Pyramid cookiecutters include a default file. The file contains declarations which tell it to include files like *.pt, *.css and *.js in the generated tarball. If you include files with extensions other than the files named in the project's and you don't make use of a Setuptools-compatible version control system, you'll need to edit the file and include the statements necessary to include your new files. See for more information about how to do this.

You can also delete from your project and rely on a :term:`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 rerun 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 :term:`Setuptools` add-on such as setuptools-git or setuptools-hg for this behavior to work properly.

.. index::

The file is a :term:`Setuptools` setup file. It is meant to be used to define requirements for installing dependencies for your package and testing, as well as distributing your application.

Note is the de facto standard which Python developers use to distribute their reusable code. You can read more about files and their usage in the Python Packaging User Guide and Setuptools documentation.

Our generated looks like this:

.. literalinclude:: myproject/
   :language: python

The file calls the :term:`Setuptools` setup function, which does various things depending on the arguments passed to pip on the command line.

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 :term:`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 name 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 files appended together. The classifiers field is a list of Trove classifiers describing your application. author and 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=False 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. install_requires indicates that this package depends on the pyramid package. extras_require is a Python dictionary that defines what is required to be installed for running tests. We examined entry_points 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 file 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:

$VENV/bin/python sdist

This will create a tarball of your application in a dist subdirectory named myproject-0.0.tar.gz. You can send this tarball to other people who want to install and use your application.

.. index::
   single: package

The myproject :term:`Package`

The myproject :term:`package` lives inside the myproject :term:`project`. It contains:

  1. An file signifies that this is a Python :term:`package`. It also contains code that helps users run the application, including a main function which is used as a entry point for commands such as pserve, pshell, pviews, and others.
  2. A templates directory, which contains :term:`Jinja2` (or other types of) templates.
  3. A module, which contains unit test code for the application.
  4. A module, which contains routing code for the application.
  5. A views package, which contains view code for the application.
  6. A static directory, which contains static files, including images and CSS.

These are purely conventions established by the cookiecutter. :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.

.. index::

We need a small Python module that configures our application and which advertises an entry point for use by our :term:`PasteDeploy` .ini file. This is the file named The presence of an also informs Python that the directory which contains it is a package.

.. literalinclude:: myproject/myproject/
   :language: python

  1. Line 1 imports the :term:`Configurator` class from :mod:`pyramid.config` that we use later.

  2. Lines 4-12 define a function named main that returns a :app:`Pyramid` WSGI application. This function is meant to be called by the :term:`PasteDeploy` framework as a result of running pserve.

    The main function configures the application.

    Line 7 opens a context manager with an instance of a :term:`Configurator`.

    Line 8 adds support for Jinja2 templating bindings, allowing us to specify renderers with the .jinja2 extension.

    Line 9 includes the module.

    Line 10 calls config.scan(), which picks up view registrations declared elsewhere in the package (in this case, in the module).

    Line 11 returns a :term:`WSGI` application to the caller of the function (Pyramid's pserve).

.. seealso::

   See :ref:`the_startup_process` for more about the application's :ref:`settings <startup_settings>` and ``main``\'s :ref:`arguments <startup_constructor_arguments>` and statements.

.. index::

The module gets included by the main function in our It registers a view and a route.

.. literalinclude:: myproject/myproject/
    :language: python

Line 2 registers a static view, which will serve up the files from the myproject:static :term:`asset specification` (the static directory of the myproject package).

Line 3 adds a :term:`route` to the configuration. This route is later used by a view in the views module.

.. index::

views package

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`.

Our project has a views package by virtue of it being a directory containing an file. This file happens to have no content, although it could as a project develops.

We have two view modules in the views package. Let's look at

.. literalinclude:: myproject/myproject/views/
   :language: python

Lines 4-6 define and register a :term:`view callable` named my_view. The function named my_view is decorated with a view_config decorator (which is processed by the config.scan() line in our The view_config decorator asserts that this view be found when a :term:`route` named home is matched. In our case, because our maps the route named home to the URL pattern /, this route will match when a visitor visits the root URL. The view_config decorator 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 ../templates/mytemplate.jinja2, which is an :term:`asset specification` that specifies the mytemplate.jinja2 file within the templates directory of the myproject package. The asset specification could have also been specified as myproject:templates/mytemplate.jinja2; the leading package name and colon is optional. The template file pointed to is a :term:`Jinja2` template file (templates/mytemplate.jinja2).

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 is configured to invoke a :term:`renderer` on a template. The dictionary the view returns (on line 6) provides the value the renderer substitutes into the template when generating HTML. The renderer then returns the HTML in a :term:`response`.


Dictionaries provide values to :term:`template`s.

Now let's look at

.. literalinclude:: myproject/myproject/views/
   :language: python

This file is similar to It merely returns a 404 response status and an empty dictionary to the template at ../templates/404.jinja2.


When the application is run with the cookiecutter's :ref:`default development.ini <myproject_ini>` configuration, :ref:`logging is set up <myproject_ini_logging>` to aid debugging. If an exception is raised, uncaught tracebacks are displayed after the startup messages on :ref:`the console running the server <running_the_project_application>`. Also print() statements may be inserted into the application for debugging to send output to this console.


development.ini has a setting that controls how templates are reloaded, pyramid.reload_templates.

  • When set to True (as in the cookiecutter development.ini), changed templates automatically reload without a server restart. This is convenient while developing, but slows template rendering speed.
  • When set to False (the default value), changing templates requires a server restart to reload them. Production applications should use pyramid.reload_templates = False.
.. seealso::

    See also :ref:`views_which_use_a_renderer` for more information about how
    views, renderers, and templates relate and cooperate.

.. seealso::

    Pyramid can also dynamically reload changed Python files.  See also

.. seealso::

    See also the :ref:`debug_toolbar`, which provides interactive access to
    your application's internals and, should an exception occur, allows
    interactive access to traceback execution stack frames from the Python

.. index::
   single: static directory


This directory contains static assets which support the layout.jinja2 template. It includes CSS and images.


This is the base layout content. It contains a single marker for content block. Other templates inherit its content, providing layout for the web application. Its contents are too long to show here, but here is an excerpt:

.. literalinclude:: myproject/myproject/templates/layout.jinja2
   :language: jinja
   :lines: 34-38


This is the content :term:`Jinja2` template that exists in the project. It is referenced by the call to @view_config as the renderer of the my_view view callable in the views/ file. See :ref:`views_which_use_a_renderer` for more information about renderers. It inherits ("extends") the HTML provided by layout.jinja2, replacing the content block with its own content.

.. literalinclude:: myproject/myproject/templates/mytemplate.jinja2
   :language: jinja

Templates are accessed and used by view configurations and sometimes by view functions themselves. See :ref:`templates_used_directly` and :ref:`templates_used_as_renderers`.


This template is similar to mytemplate.jinja2, but with a few differences. It is referenced by the call to @notfound_view_config as the renderer of the notfound_view view callable in the views/ file. It inherits the HTML provided by layout.jinja2, replacing the content block with its own content.

.. literalinclude:: myproject/myproject/templates/404.jinja2
   :language: jinja

.. index::

The module includes tests for your application.

.. literalinclude:: myproject/myproject/
   :language: python

This sample file has one unit test and one functional test defined within it. These tests are executed when you run pytest -q. 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 for convenience and example.

See :ref:`testing_chapter` for more information about writing :app:`Pyramid` unit tests.

.. index::
   pair: modifying; package structure

Modifying Package Structure

It is best practice for your application's code layout to not stray too much from accepted Pyramid cookiecutter 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 cookiecutter are in no way magical or required. Despite the choices made for you by any cookiecutter, 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 starter cookiecutter would have you create a views directory, and add a single file for each view or collection of related views. However, you might be more comfortable creating a single module in your package and add view functions to it.

Whatever structure you prefer, as long as you use the @view_config directive to register views in conjunction with config.scan(), they will be picked up automatically when the application is restarted.

Using the Interactive Shell

It is possible to use the pshell command to load a Python interpreter prompt with a similar configuration as would be loaded if you were running your Pyramid application via pserve. This can be a useful debugging tool. See :ref:`interactive_shell` for more details.

What Is This pserve Thing

The code generated by a :app:`Pyramid` cookiecutter assumes that you will be using the pserve command to start your application while you do development. pserve is a command that reads a :term:`PasteDeploy` .ini file (e.g., development.ini), and configures a server to serve a :app:`Pyramid` application based on the data in the file.

pserve is by no means the only way to start up and serve a :app:`Pyramid` application. As we saw in :ref:`firstapp_chapter`, pserve needn't be invoked at all to run a :app:`Pyramid` application. The use of pserve to run a :app:`Pyramid` application is purely conventional based on the output of its cookiecutter. But we strongly recommend using pserve while developing your application because many other convenience introspection commands (such as pviews, prequest, proutes, and others) are also implemented in terms of configuration availability of this .ini file format. It also configures Pyramid logging and provides the --reload switch for convenient restarting of the server when code changes.

Using an Alternate WSGI Server

Pyramid cookiecutters generate projects which use the :term:`Waitress` WSGI server. Waitress is a server that is suited for development and light production usage. It's not the fastest nor the most featureful WSGI server. Instead, its main feature is that it works on all platforms that Pyramid needs to run on, making it a good choice as a default server from the perspective of Pyramid's developers.

Any WSGI server is capable of running a :app:`Pyramid` application. But we suggest you stick with the default server for development, and that you wait to investigate other server options until you're ready to deploy your application to production. Unless for some reason you need to develop on a non-local system, investigating alternate server options is usually a distraction until you're ready to deploy. But we recommend developing using the default configuration on a local system that you have complete control over; it will provide the best development experience.

One popular production alternative to the default Waitress server is :term:`mod_wsgi`. You can use mod_wsgi to serve your :app:`Pyramid` application using the Apache web server rather than any "pure-Python" server like Waitress. It is fast and featureful. See :ref:`modwsgi_tutorial` for details.

Another good production alternative is :term:`Green Unicorn` (aka gunicorn). It's faster than Waitress and slightly easier to configure than mod_wsgi, although it depends, in its default configuration, on having a buffering HTTP proxy in front of it. It does not, as of this writing, work on Windows.

Automatically Reloading Your Code

During development, it can be really useful to automatically have the webserver restart when you make changes. pserve has a --reload switch to enable this. It uses the hupper package to enable this behavior. When your code crashes, hupper will wait for another change or the SIGHUP signal before restarting again.

inotify support

By default hupper will poll the filesystem for changes to all Python code. This can be pretty inefficient in larger projects. To be nicer to your hard drive, you should install the watchdog package in development. hupper will automatically use watchdog to more efficiently poll the filesystem.

Monitoring Custom Files

By default, pserve --reload will monitor all imported Python code (everything in sys.modules) as well as the config file passed to pserve (e.g., development.ini). You can instruct pserve to watch other files for changes as well by defining a [pserve] section in your configuration file. For example, let's say your application loads the favicon.ico file at startup and stores it in memory to efficiently serve it many times. When you change it, you want pserve to restart:

watch_files =

Paths may be absolute or relative to the configuration file. They may also be an :term:`asset specification`. These paths are passed to hupper, which has some basic support for globbing. Acceptable glob patterns depend on the version of Python being used.

You can’t perform that action at this time.