.. _project_narr: 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 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 ``pcreate`` command that is installed as part of Pyramid. .. index:: single: scaffolds single: starter scaffold single: zodb scaffold single: alchemy scaffold .. _additional_paster_scaffolds: Scaffolds Included with :app:`Pyramid` ------------------------------------------------ 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`). The included scaffolds are these: ``starter`` URL mapping via :term:`URL dispatch` and no persistence mechanism. ``zodb`` URL mapping via :term:`traversal` and persistence via :term:`ZODB`. *Note that, as of this writing, this scaffold will not run under Python 3, only under Python 2.* ``alchemy`` URL mapping via :term:`URL dispatch` and persistence via :term:`SQLAlchemy` .. index:: single: creating a project single: project .. _creating_a_project: Creating the Project -------------------- In :ref:`installing_chapter`, you created a virtual Python environment via the ``virtualenv`` command. To start a :app:`Pyramid` :term:`project`, use the ``pcreate`` command installed within the virtualenv. We'll choose the ``starter`` scaffold for this purpose. When we invoke ``pcreate``, it will create a directory that represents our project. In :ref:`installing_chapter` we called the virtualenv directory ``env``; the following commands assume that our current working directory is the ``env`` directory. On UNIX: .. code-block:: text $ bin/pcreate -s starter MyProject Or on Windows: .. code-block:: text > Scripts\pcreate -s starter MyProject The above command uses the ``pcreate`` command to create a project with the ``starter`` scaffold. To use a different scaffold, such as ``alchemy``, you'd just change the ``-s`` argument value. For example, on UNIX: .. code-block:: text $ bin/pcreate -s alchemy MyProject Or on Windows: .. code-block:: text > Scripts\pcreate -s alchemy MyProject Here's sample output from a run of ``pcreate`` on UNIX for a project we name ``MyProject``: .. code-block:: text $ bin/pcreate -s starter MyProject Creating template pyramid Creating directory ./MyProject # ... more output ... Running /Users/chrism/projects/pyramid/bin/python setup.py egg_info As a result of invoking the ``pcreate`` command, a directory named ``MyProject`` is created. That directory is a :term:`project` directory. The ``setup.py`` file in that directory can be used to distribute your application, or install your application for deployment or development. A ``.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`` (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. We created this project within an ``env`` virtualenv 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, and you don't need to put it within a virtualenv 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 ``pcreate`` to create a project with the same as a Python standard library component. In particular, this means you should avoid using names 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: setup.py 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:`virtualenv` you created during :ref:`installing_chapter` to invoke the command ``python setup.py develop`` The file named ``setup.py`` will be in the root of the pcreate-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: .. code-block:: text $ cd MyProject $ ../bin/python setup.py develop Or on Windows: .. code-block:: text > cd MyProject > ..\Scripts\python.exe setup.py develop Elided output from a run of this command on UNIX is shown below: .. code-block:: text $ 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 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 should invoke them using the Python interpreter from the :term:`virtualenv` you created during :ref:`installing_chapter` (the ``python`` command that lives in the ``bin`` directory of your virtualenv). On UNIX: .. code-block:: text $ ../bin/python setup.py test -q Or on Windows: .. code-block:: text > ..\Scripts\python.exe setup.py test -q Here's sample output from a test run on UNIX: .. code-block:: text $ ../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 .. note:: The ``-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 ``pcreate`` generated project. Within a project generated by the ``starter`` scaffold, a single sample test exists. .. index:: single: running an application single: pserve single: reload single: startup Running The Project Application ------------------------------- 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: .. code-block:: text $ ../bin/pserve development.ini On Windows: .. code-block:: text > ..\Scripts\pserve development.ini Here's sample output from a run of ``pserve`` on UNIX: .. code-block:: text $ ../bin/pserve 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 pressing ``Ctrl-C``. The default server used to run your Pyramid application when a project is created from a scaffold 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 nondefault 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. You can change the port on which the server runs on by changing the ``development.ini`` file. For example, you can change the ``port = 6543`` line in the ``development.ini`` file's ``[server:main]`` section to ``port = 8080`` to run the server on port 8080 instead of port 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`. .. _reloading_code: 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: .. code-block:: text $ ../bin/pserve development.ini --reload Starting subprocess with file monitor Starting server in PID 16601. serving on http://0.0.0.0:6543 Now if you make a change to any of your project's ``.py`` files or ``.ini`` files, you'll see the server restart automatically: .. code-block:: text development.ini changed; reloading... -------------------- Restarting -------------------- Starting server in PID 16602. serving on http://0.0.0.0:6543 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: .. image:: project.png This is the page shown by default when you visit an unmodified ``pcreate`` generated ``starter`` application in a browser. .. index:: single: debug toolbar .. _debug_toolbar: 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 image again. .. image:: project-debug.png If you don't see the debug toolbar image on the right hand top 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`` (``127.0.0.1``) can see the debug toolbar. To allow your browser on a remote system to access the server, add the 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 ``192.168.1.1``, you'd add something like this to enable the toolbar when your system contacts Pyramid: .. code-block:: ini [app:main] # .. other settings ... debugtoolbar.hosts = 192.168.1.1 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 ``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: .. code-block:: ini :linenos: [app:main] ... pyramid.includes = pyramid_debugtoolbar Put a hash mark at the beginning of the ``pyramid_debugtoolbar`` line: .. code-block:: ini :linenos: [app:main] ... pyramid.includes = # pyramid_debugtoolbar 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 the hash mark anywhere except the first column instead, for example like this: .. code-block:: ini :linenos: [app:main] ... pyramid.includes = #pyramid_debugtoolbar When you attempt to restart the application with a section like the abvoe you'll receive an error that ends something like this, and the application will not start: .. code-block:: text ImportError: No module named #pyramid_debugtoolbar .. index:: single: project structure The Project Structure --------------------- The ``starter`` scaffold generated a :term:`project` (named ``MyProject``), which contains a Python :term:`package`. The package is *also* named ``myproject``, but it's lowercased; the scaffold generates a project which contains a package that shares its name except for case. All :app:`Pyramid` ``pcreate`` -generated projects share a similar structure. The ``MyProject`` project we've generated has the following directory structure: .. code-block:: text MyProject/ |-- CHANGES.txt |-- development.ini |-- MANIFEST.in |-- myproject | |-- __init__.py | |-- static | | |-- favicon.ico | | |-- logo.png | | `-- pylons.css | |-- templates | | `-- mytemplate.pt | |-- tests.py | `-- views.py |-- production.ini |-- README.txt |-- setup.cfg `-- setup.py 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. #. ``CHANGES.txt`` describes the changes you've made to the application. It is conventionally written in :term:`ReStructuredText` format. #. ``README.txt`` describes the application in general. It is conventionally written in :term:`ReStructuredText` format. #. ``development.ini`` is a :term:`PasteDeploy` configuration file that can be used to execute your application during development. #. ``production.ini`` is a :term:`PasteDeploy` configuration file that can be used to execute your application in a production configuration. #. ``setup.cfg`` is a :term:`setuptools` configuration file used by ``setup.py``. #. ``MANIFEST.in`` is a :term:`distutils` "manifest" file, naming which files should be included in a source distribution of the package when ``python setup.py sdist`` is run. #. ``setup.py`` is the file you'll use to test and distribute your application. It is a standard :term:`setuptools` ``setup.py`` file. .. index:: single: PasteDeploy single: ini file .. _MyProject_ini: ``development.ini`` ~~~~~~~~~~~~~~~~~~~ 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 :linenos: 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 ``__init__.py`` module. You can provide startup-time configuration parameters to your application by adding more settings to this section. .. note:: 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``, :term:`Chameleon` and :term:`Mako` template changes will not require an application restart to be detected. See :ref:`reload_templates_section` 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 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. 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 all interfaces (``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`` and ``# 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 ``pserve`` or ``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 :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 ``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:: single: MANIFEST.in ``MANIFEST.in`` ~~~~~~~~~~~~~~~ The ``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 ``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 http://docs.python.org/distutils/sourcedist.html#the-manifest-in-template 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 scaffolds 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. 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 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. .. index:: single: setup.py ``setup.py`` ~~~~~~~~~~~~ The ``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. .. note:: ``setup.py`` is the defacto standard which Python developers use to distribute their reusable code. You can read more about ``setup.py`` files and their usage in the `Setuptools documentation `_ and `The Hitchhiker's Guide to Packaging `_. Our generated ``setup.py`` looks like this: .. literalinclude:: MyProject/setup.py :language: python :linenos: The ``setup.py`` file calls the setuptools ``setup`` function, which does various things depending on the arguments passed to ``setup.py`` 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 file 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`` 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`` and ``tests_require`` indicate that this package depends on the ``pyramid`` package. ``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 ``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: .. code-block:: text $ python setup.py sdist This will create a tarball of your application in a ``dist`` subdirectory named ``MyProject-0.1.tar.gz``. You can send this tarball to other people who want to install and use your application. .. index:: single: setup.cfg ``setup.cfg`` ~~~~~~~~~~~~~ The ``setup.cfg`` file is a :term:`setuptools` configuration file. It contains various settings related to testing and internationalization: Our generated ``setup.cfg`` looks like this: .. literalinclude:: MyProject/setup.cfg :language: guess :linenos: The values in the default setup file allow various commonly-used internationalization commands and testing commands to work more smoothly. .. index:: single: package The ``myproject`` :term:`Package` --------------------------------- The ``myproject`` :term:`package` lives inside the ``MyProject`` :term:`project`. It contains: #. An ``__init__.py`` 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. #. A ``templates`` directory, which contains :term:`Chameleon` (or other types of) templates. #. A ``tests.py`` module, which contains unit test code for the application. #. A ``views.py`` module, 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. .. index:: single: __init__.py .. _init_py: ``__init__.py`` ~~~~~~~~~~~~~~~ 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 ``__init__.py``. The presence of an ``__init__.py`` also informs Python that the directory which contains it is a *package*. .. literalinclude:: MyProject/myproject/__init__.py :language: python :linenos: #. Line 1 imports the :term:`Configurator` class from :mod:`pyramid.config` that we use later. #. Lines 3-10 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``. Within this function, application configuration is performed. Line 6 creates an instance of a :term:`Configurator`. Line 7 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 8 adds a :term:`route` to the configuration. This route is later used by a view in the ``views`` module. Line 9 calls ``config.scan()``, which picks up view registrations declared elsewhere in the package (in this case, in the ``views.py`` module). Line 10 returns a :term:`WSGI` application to the caller of the function (Pyramid's pserve). .. index:: single: views.py ``views.py`` ~~~~~~~~~~~~ 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`. .. literalinclude:: MyProject/myproject/views.py :language: python :linenos: Lines 3-5 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 ``__init__.py``). The view_config decorator asserts that this view be found when a :term:`route` named ``home`` is matched. In our case, because our ``__init__.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 ``templates/mytemplate.pt``, which is a :term:`asset specification` that specifies the ``mytemplate.pt`` file within the ``templates`` directory of the ``myproject`` package. The asset specification could have also been specified as ``myproject:templates/mytemplate.pt``; the leading package name and colon is optional. The template file it actually points to is a :term:`Chameleon` ZPT template file. 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 (``templates/my_template.pt``). See :ref:`views_which_use_a_renderer` for more information about how views, renderers, and templates relate and cooperate. .. note:: Because our ``development.ini`` has a ``pyramid.reload_templates = 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 ``pyramid.reload_templates`` to ``false`` to increase the speed at which templates may be rendered. .. index:: single: static directory ``static`` ~~~~~~~~~~ This directory contains static assets which support the ``mytemplate.pt`` template. It includes CSS and images. ``templates/mytemplate.pt`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 ``@view_config`` as the ``renderer`` of the ``my_view`` view callable in the ``views.py`` file. See :ref:`views_which_use_a_renderer` for more information about renderers. 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`. .. index:: single: tests.py ``tests.py`` ~~~~~~~~~~~~ The ``tests.py`` module includes unit tests for your application. .. literalinclude:: MyProject/myproject/tests.py :language: python :linenos: This sample ``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 example. See :ref:`testing_chapter` for more information about writing :app:`Pyramid` unit tests. .. index:: pair: modifying; package structure .. _modifying_package_structure: 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 ``starter`` scaffold would have you add view functions to the ``views.py`` module in your package. However, you might be more comfortable creating a ``views`` *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 ``myproject`` :term:`package` named ``views`` instead of within a single ``views.py`` file, you might: - Create a ``views`` directory inside your ``myproject`` package directory (the same directory which holds ``views.py``). - *Move* the existing ``views.py`` file to a file inside the new ``views`` directory named, say, ``blog.py``. - Create a file within the new ``views`` directory named ``__init__.py`` (it can be empty, this just tells Python that the ``views`` directory is a *package*. You can then continue to add view callable functions to the ``blog.py`` module, but you can also add other ``.py`` files which contain view callable functions to the ``views`` directory. As long as you use the ``@view_config`` directive to register views in conjuction 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 an :app:`Pyramid` scaffold 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 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 scaffolding. But we strongly recommend using while developing your application, because many other convenience introspection commands (such as ``pviews``, ``prequest``, ``proutes`` and others) are also implemented in terms of configuration availaibility of this ``.ini`` file format. It also configures Pyramid logging and provides the ``--reload`` switch for convenient restarting of the server when code changes. .. _alternate_wsgi_server: Using an Alternate WSGI Server ------------------------------ Pyramid scaffolds 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.