Creating a Pyramid Project¶

As we saw in Creating Your First Pyramid Application, it's possible to create a Pyramid application completely manually. However, it's usually more convenient to use our cookiecutter to generate a basic Pyramid project.

A project is a directory that contains at least one Python package. You'll use the 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 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.

See also

Pyramid cookiecutters¶

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

templating libraries (Jinja2, Chameleon, or Mako)
the persistence mechanism (no persistence mechanism, SQLAlchemy with SQLite, or ZODB)
the mechanism of mapping URLs to code (URL dispatch or traversal)

pyramid-cookiecutter-starter

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.

none: URL dispatch for routing
sqlalchemy: SQLite for persistent storage, SQLAlchemy for an ORM, URL dispatch for routing, and Alembic for database migrations
zodb: ZODB for persistent storage and traversal for routing

Creating the Project¶

In Installing Pyramid, 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 previously installed cookiecutter, 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 2.0-branch

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.
$VENV/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 project directory. The setup.py 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 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 package which holds very simple 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.

Warning

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.

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 virtual environment you created during Installing Pyramid 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 setup.py 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 setup.py develop for myproject
Successfully installed Jinja2-2.11.2 Mako-1.1.3 MarkupSafe-1.1.1 PasteDeploy-2.1.1 Pygments-2.7.3 hupper-1.10.2 myproject plaster-1.0 plaster-pastedeploy-0.7 pyramid-1.10.5 pyramid-debugtoolbar-4.9 pyramid-jinja2-2.8 pyramid-mako-1.1.0 repoze.lru-0.7 translationstring-1.4 venusian-3.0.0 waitress-1.4.4 webob-1.8.6 zope.deprecation-4.4.0 zope.interface-5.2.0

This will install a 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.

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
....
4 passed in 0.31s

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

Note

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 tests -q

See also

See pytest's documentation for How to invoke pytest or invoke pytest -h to see its full set of options.

Running the Project Application¶

See also

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 Pyramid application is not put into effect until the server restarts.

For example, on Unix:

$VENV/bin/pserve development.ini --reload
Starting monitor for PID 36224.
Starting server in PID 36224.
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:

/file-path-to/myproject/development.ini changed; reloading ...
Gracefully killing the server.
Starting monitor for PID 36286.
Starting server in PID 36286.
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.

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.

The Project Structure¶

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

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

myproject
├── .coveragerc
├── .gitignore
├── CHANGES.txt
├── MANIFEST.in
├── README.txt
├── development.ini
├── myproject
│   ├── __init__.py
│   ├── routes.py
│   ├── static
│   │   ├── pyramid-16x16.png
│   │   ├── pyramid.png
│   │   └── theme.css
│   ├── templates
│   │   ├── 404.jinja2
│   │   ├── layout.jinja2
│   │   └── mytemplate.jinja2
│   └── views
│       ├── __init__.py
│       ├── default.py
│       └── notfound.py
├── production.ini
├── pytest.ini
├── setup.py
├── testing.ini
└── tests
    ├── __init__.py
    ├── conftest.py
    ├── test_functional.py
    └── test_views.py

`tests` package¶

The conftest.py, test_functional.py, and test_views.py modules in the tests package includes tests for your application.

import os
from pyramid.paster import get_appsettings
from pyramid.scripting import prepare
from pyramid.testing import DummyRequest, testConfig
import pytest
import webtest

from myproject import main


def pytest_addoption(parser):
    parser.addoption('--ini', action='store', metavar='INI_FILE')

@pytest.fixture(scope='session')
def ini_file(request):
    # potentially grab this path from a pytest option
    return os.path.abspath(request.config.option.ini or 'testing.ini')

@pytest.fixture(scope='session')
def app_settings(ini_file):
    return get_appsettings(ini_file)

@pytest.fixture(scope='session')
def app(app_settings):
    return main({}, **app_settings)

@pytest.fixture
def testapp(app):
    testapp = webtest.TestApp(app, extra_environ={
        'HTTP_HOST': 'example.com',
    })

    return testapp

@pytest.fixture
def app_request(app):
    """
    A real request.

    This request is almost identical to a real request but it has some
    drawbacks in tests as it's harder to mock data and is heavier.

    """
    with prepare(registry=app.registry) as env:
        request = env['request']
        request.host = 'example.com'
        yield request

@pytest.fixture
def dummy_request():
    """
    A lightweight dummy request.

    This request is ultra-lightweight and should be used only when the request
    itself is not a large focus in the call-stack.  It is much easier to mock
    and control side-effects using this object, however:

    - It does not have request extensions applied.
    - Threadlocals are not properly pushed.

    """
    request = DummyRequest()
    request.host = 'example.com'

    return request

@pytest.fixture
def dummy_config(dummy_request):
    """
    A dummy :class:`pyramid.config.Configurator` object.  This allows for
    mock configuration, including configuration for ``dummy_request``, as well
    as pushing the appropriate threadlocals.

    """
    with testConfig(request=dummy_request) as config:
        yield config

def test_root(testapp):
    res = testapp.get('/', status=200)
    assert b'Pyramid' in res.body

def test_notfound(testapp):
    res = testapp.get('/badurl', status=404)
    assert res.status_code == 404

from myproject.views.default import my_view
from myproject.views.notfound import notfound_view


def test_my_view(app_request):
    info = my_view(app_request)
    assert app_request.response.status_int == 200
    assert info['project'] == 'myproject'

def test_notfound_view(app_request):
    info = notfound_view(app_request)
    assert app_request.response.status_int == 404
    assert info == {}

The sample conftest.py file contains test configuration and fixtures. The sample test_functional.py file has two functional tests defined within it. The sample test_views.py file has two unit tests 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 Pyramid. These files are provided only for convenience and example.

See Unit, Integration, and Functional Testing for more information about writing Pyramid unit tests.

The `myproject` Project ¶

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

.coveragerc configures coverage when running tests.
.gitignore tells git which files and directories to ignore from source code version control.
CHANGES.txt describes the changes you've made to the application. It is conventionally written in reStructuredText format.
MANIFEST.in is a distutils "manifest" file, naming which files should be included in a source distribution of the package when python setup.py sdist is run.
README.txt describes the application in general. It is conventionally written in reStructuredText format.
development.ini is a PasteDeploy configuration file that can be used to execute your application during development.
production.ini is a PasteDeploy configuration file that can be used to execute your application in a production configuration.
pytest.ini is a configuration file for running tests.
setup.py is the file you'll use to test and distribute your application. It is a standard Setuptools setup.py file.
testing.ini is a PasteDeploy configuration file that can be used to execute your application's tests.
tests package which contains unit and functional test code for the application.

`development.ini`¶

The development.ini file is a 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:

###
# app configuration
# https://docs.pylonsproject.org/projects/pyramid/en/latest/narr/environment.html
###

[app:main]
use = egg:myproject

pyramid.reload_templates = true
pyramid.debug_authorization = false
pyramid.debug_notfound = false
pyramid.debug_routematch = false
pyramid.default_locale_name = en
pyramid.includes =
    pyramid_debugtoolbar

# By default, the toolbar only appears for clients from IP addresses
# '127.0.0.1' and '::1'.
# debugtoolbar.hosts = 127.0.0.1 ::1

###
# wsgi server configuration
###

[server:main]
use = egg:waitress#main
listen = localhost:6543

###
# logging configuration
# https://docs.pylonsproject.org/projects/pyramid/en/latest/narr/logging.html
###

[loggers]
keys = root, myproject

[handlers]
keys = console

[formatters]
keys = generic

[logger_root]
level = INFO
handlers = console

[logger_myproject]
level = DEBUG
handlers =
qualname = myproject

[handler_console]
class = StreamHandler
args = (sys.stderr,)
level = NOTSET
formatter = generic

[formatter_generic]
format = %(asctime)s %(levelname)-5.5s [%(name)s:%(lineno)s][%(threadName)s] %(message)s

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 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 __init__.py module. You can provide startup-time configuration parameters to your application by adding more settings to this section.

See also

See Entry Points and PasteDeploy .ini Files 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 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 Automatically Reloading Templates for more information.

Warning

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 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 Pyramid application. See Environment Variables and .ini File Settings 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 (127.0.0.1).

The sections after # logging configuration represent Python's standard library 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 Logging.

See the PasteDeploy documentation for more information about other types of things you can put into this .ini file, such as other applications, middleware, and alternate WSGI server implementations.

`production.ini`¶

The production.ini file is a 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.

`testing.ini`¶

The testing.ini file is a PasteDeploy configuration file with a purpose much like that of development.ini. It is similar to development.ini, but is optimized to reduce test execution time. It disables the debug toolbar and automatic reloading of templates, as these slow down test execution. This file is appropriate to use instead of development.ini when you run your application's tests.

`MANIFEST.in`¶

The MANIFEST.in file is a distutils configuration file which specifies the non-Python files that should be included when a distribution of your Pyramid project is created when you run python setup.py sdist. Due to the information contained in the default MANIFEST.in, 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 the Python Packaging Authority's Python Packaging User Guide Including files in source distributions with MANIFEST.in for more information about the syntax and usage of MANIFEST.in.

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 generated by 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 the sdist machinery to include *.pt files, the myproject/templates/mytemplate.pt file would not be included in the generated tarball.

Projects generated by Pyramid cookiecutters include a default MANIFEST.in file. The MANIFEST.in 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 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. In the aforementioned Python Packaging User Guide, see MANIFEST.in commands 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 rerun 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-git or setuptools-hg for this behavior to work properly.

`setup.py`¶

The setup.py file is a 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

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

Our generated setup.py looks like this:

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 = [
    'plaster_pastedeploy',
    'pyramid',
    'pyramid_jinja2',
    'pyramid_debugtoolbar',
    'waitress',
]

tests_require = [
    'WebTest',
    'pytest',
    'pytest-cov',
]

setup(
    name='myproject',
    version='0.0',
    description='myproject',
    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 pyramid pylons',
    packages=find_packages(exclude=['tests']),
    include_package_data=True,
    zip_safe=False,
    extras_require={
        'testing': tests_require,
    },
    install_requires=requires,
    entry_points={
        'paste.app_factory': [
            'main = myproject:main',
        ],
    },
)

The setup.py file calls the 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 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). keywords are keywords that describe your project. packages=find_packages(exclude=['tests']) 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. extras_require is a Python dictionary that defines what is required to be installed for running tests. install_requires indicates that this package depends on the pyramid package. 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 setup.py 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 setup.py 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.

The `myproject` Package ¶

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

An __init__.py file signifies that this is a Python 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.
A templates directory, which contains Jinja2 (or other types of) templates.
A routes.py module, which contains routing code for the application.
A views package, which contains view code for the application.
A static directory, which contains static files, including images and CSS.

These are purely conventions established by the cookiecutter. 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.

`init.py`¶

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

from pyramid.config import Configurator


def main(global_config, **settings):
    """ This function returns a Pyramid WSGI application.
    """
    with Configurator(settings=settings) as config:
        config.include('pyramid_jinja2')
        config.include('.routes')
        config.scan()
    return config.make_wsgi_app()

Line 1 imports the Configurator class from pyramid.config that we use later.
Lines 4-11 define a function named main that returns a Pyramid WSGI application. This function is meant to be called by the 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 Configurator.

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

Line 9 includes the routes.py module.

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

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

See also

See The Startup Process for more about the application's settings and main's arguments and statements.

`routes.py`¶

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

def includeme(config):
    config.add_static_view('static', 'static', cache_max_age=3600)
    config.add_route('home', '/')

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

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

`views` package¶

Much of the heavy lifting in a Pyramid application is done by view callables. A view callable is the main tool of a Pyramid web application developer; it is a bit of code which accepts a request and which returns a response.

Our project has a views package by virtue of it being a directory containing an __init__.py file. This __init__.py 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 default.py.

from pyramid.view import view_config


@view_config(route_name='home', renderer='myproject:templates/mytemplate.jinja2')
def my_view(request):
    return {'project': 'myproject'}

Lines 4-6 define and register a 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 __init__.py). The view_config decorator asserts that this view be found when a route named home is matched. In our case, because our routes.py 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 myproject:templates/mytemplate.jinja2, which is an asset specification that specifies the mytemplate.jinja2 file within the templates directory of the myproject package. There is a second form of asset specification: a relative asset specification. Instead of using an "absolute" asset specification which includes the package name, in certain circumstances you can omit the package name from the specification. For example, you might be able to use ../templates/mytemplate.jinja2. The template file pointed to is a Jinja2 template file (templates/mytemplate.jinja2).

This view callable function is handed a single piece of information: the request. The request is an instance of the WebOb Request class representing the browser's request to our server.

This view is configured to invoke a 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 response.

Note

Dictionaries provide values to templates.

Now let's look at notfound.py.

from pyramid.view import notfound_view_config


@notfound_view_config(renderer='myproject:templates/404.jinja2')
def notfound_view(request):
    request.response.status = 404
    return {}

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

Note

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

Note

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.

See also

See also Writing View Callables Which Use a Renderer for more information about how views, renderers, and templates relate and cooperate.

See also

Pyramid can also dynamically reload changed Python files. See also Reloading Code.

See also

See also the The 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 interpreter.

`static`¶

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

`templates/layout.jinja2`¶

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:

          <div class="col-md-10">
            {% block content %}
                <p>No content</p>
            {% endblock content %}
          </div>

`templates/mytemplate.jinja2`¶

This is the content 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/default.py file. See Writing View Callables 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.

{% extends "layout.jinja2" %}

{% block content %}
<div class="content">
  <h1><span class="font-semi-bold">Pyramid</span> <span class="smaller">Starter project</span></h1>
  <p class="lead">Welcome to <span class="font-normal">{{project}}</span>, a&nbsp;Pyramid application generated&nbsp;by<br><span class="font-normal">Cookiecutter</span>.</p>
</div>
{% endblock content %}

Templates are accessed and used by view configurations and sometimes by view functions themselves. See Using Templates Directly and Templates Used as Renderers via Configuration.

`templates/404.jinja2`¶

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/notfound.py file. It inherits the HTML provided by layout.jinja2, replacing the content block with its own content.

{% extends "layout.jinja2" %}

{% block content %}
<div class="content">
  <h1><span class="font-semi-bold">Pyramid</span> <span class="smaller">Starter project</span></h1>
  <p class="lead"><span class="font-semi-bold">404</span> Page Not Found</p>
</div>
{% endblock content %}

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 add_view() requires you to pass a 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 views.py 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 pshell: The Interactive Shell for more details.

What Is This `pserve` Thing¶

The code generated by a 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 PasteDeploy .ini file (e.g., development.ini), and configures a server to serve a Pyramid application based on the data in the file.

pserve is by no means the only way to start up and serve a Pyramid application. As we saw in Creating Your First Pyramid Application, pserve needn't be invoked at all to run a Pyramid application. The use of pserve to run a 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 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 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 mod_wsgi. You can use mod_wsgi to serve your Pyramid application using the Apache web server rather than any "pure-Python" server like Waitress. It is fast and featureful. See Running a Pyramid Application under mod_wsgi for details.

Another good production alternative is 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 either the watchman or watchdog package in development. hupper will use, in order of preference for efficiency, if available, watchman, watchdog, or finally polling to detect changes to 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:

[pserve]
watch_files =
    myproject/static/favicon.ico

Paths may be absolute or relative to the configuration file. They may also be an 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.

Creating a Pyramid Project¶

Pyramid cookiecutters¶

Creating the Project¶

Installing your Newly Created Project for Development¶

Running the Tests for Your Application¶

Running the Project Application¶

Reloading Code¶

Viewing the Application¶

The Project Structure¶

`tests` package¶

The `myproject` Project ¶

`development.ini`¶

`production.ini`¶

`testing.ini`¶

`MANIFEST.in`¶

`setup.py`¶

The `myproject` Package ¶

`init.py`¶

`routes.py`¶

`views` package¶

`static`¶

`templates/layout.jinja2`¶

`templates/mytemplate.jinja2`¶

`templates/404.jinja2`¶

Modifying Package Structure¶

Using the Interactive Shell¶

What Is This `pserve` Thing¶

Using an Alternate WSGI Server¶

Automatically Reloading Your Code¶

inotify support¶

Monitoring Custom Files¶

Table of Contents

Previous topic

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This Page

Creating a Pyramid Project¶

Pyramid cookiecutters¶

Creating the Project¶

Installing your Newly Created Project for Development¶

Running the Tests for Your Application¶

Running the Project Application¶

Reloading Code¶

Viewing the Application¶

The Debug Toolbar¶

The Project Structure¶

tests package¶

The myproject Project¶

development.ini¶

production.ini¶

testing.ini¶

MANIFEST.in¶

setup.py¶

The myproject Package¶

__init__.py¶

routes.py¶

views package¶

static¶

templates/layout.jinja2¶

templates/mytemplate.jinja2¶

templates/404.jinja2¶

Modifying Package Structure¶

Using the Interactive Shell¶

What Is This pserve Thing¶

Using an Alternate WSGI Server¶

Automatically Reloading Your Code¶

inotify support¶

Monitoring Custom Files¶

`tests` package¶

The `myproject` Project ¶

`development.ini`¶

`production.ini`¶

`testing.ini`¶

`MANIFEST.in`¶

`setup.py`¶

The `myproject` Package ¶

`init.py`¶

`routes.py`¶

`views` package¶

`static`¶

`templates/layout.jinja2`¶

`templates/mytemplate.jinja2`¶

`templates/404.jinja2`¶

What Is This `pserve` Thing¶