.. _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 *template* 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 template 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 a package is more easily extended with new code. 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 templates that you can use to generate a project. Each template makes different configuration assumptions about what type of application you're trying to construct. These templates are rendered using the :term:`PasteDeploy` ``paster`` script, and so therefore they are often referred to as "paster templates". .. index:: single: paster templates single: pyramid_starter paster template single: pyramid_zodb paster template single: pyramid_alchemy paster template single: pyramid_routesalchemy paster template .. _additional_paster_templates: Paster Templates Included with :app:`Pyramid` ------------------------------------------------ The convenience ``paster`` templates included with :app:`Pyramid` differ from each other on a number of axes: - the persistence mechanism they offer (no persistence mechanism, :term:`ZODB`, or :term:`SQLAlchemy`). - the mechanism they use to map URLs to code (:term:`traversal` or :term:`URL dispatch`). - whether or not the ``pyramid_beaker`` library is relied upon as the sessioning implementation (as opposed to no sessioning or default sessioning). The included templates are these: ``pyramid_starter`` URL mapping via :term:`traversal` and no persistence mechanism. ``pyramid_zodb`` URL mapping via :term:`traversal` and persistence via :term:`ZODB`. ``pyramid_routesalchemy`` URL mapping via :term:`URL dispatch` and persistence via :term:`SQLAlchemy` ``pyramid_alchemy`` URL mapping via :term:`traversal` and persistence via :term:`SQLAlchemy` .. note:: At this time, each of these templates uses the :term:`Chameleon` templating system, which is incompatible with both Jython and PyPy. To use paster templates to build applications which will run on Jython and PyPy, you can try the ``pyramid_jinja2_starter`` template which ships as part of the :term:`pyramid_jinja2` package or the ``pyramid_sqla`` paster template which ships with the :term:`pyramid_sqla` package (it uses Mako), both available from :term:`PyPI`. You can also just use the above paster templates to build a skeleton and replace the Chameleon template it includes with a :term:`Mako` analogue. Rather than use any of the above templates, Pylons 1 users may feel more comfortable installing the :term:`pyramid_sqla` add-on package, which provides a paster template named ``pyramid_sqla``. This paster template configures a Pyramid application in a "Pylons-esque" way, including the use of a :term:`view handler` to map URLs to code (it's much like a Pylons "controller"). .. 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 ``paster`` facility installed within the virtualenv. In :ref:`installing_chapter` we called the virtualenv directory ``env``; the following command assumes that our current working directory is that directory. We'll choose the ``pyramid_starter`` template for this purpose. .. code-block:: text $ bin/paster create -t pyramid_starter The above command uses the ``paster`` command to create a project using the ``pyramid_starter`` template. The ``paster create`` command creates project from a template. To use a different template, such as ``pyramid_routesalchemy``, you'd just change the last argument. For example: .. code-block:: text $ bin/paster create -t pyramid_routesalchemy ``paster create`` will ask you a single question: the *name* of the project. You should use a string without spaces and with only letters in it. Here's sample output from a run of ``paster create`` for a project we name ``MyProject``: .. code-block:: text $ bin/paster create -t pyramid_starter Selected and implied templates: pyramid#pyramid_starter pyramid starter project Enter project name: MyProject Variables: egg: MyProject package: myproject project: MyProject Creating template pyramid Creating directory ./MyProject # ... more output ... Running /Users/chrism/projects/pyramid/bin/python setup.py egg_info .. note:: You can skip the interrogative question about a project name during ``paster create`` by adding the project name to the command line, e.g. ``paster create -t pyramid_starter MyProject``. .. note:: You may encounter an error when using ``paster create`` if a dependent Python package is not installed. This will result in a traceback ending in ``pkg_resources.DistributionNotFound: ``. Simply run ``bin/easy_install``, with the missing package name from the error message to work around this issue. As a result of invoking the ``paster create`` command, a project is created in a directory named ``MyProject``. That directory is a :term:`project` directory. The ``setup.py`` file in that directory can be used to distribute your application, or install your application for deployment or development. A :term:`PasteDeploy` ``.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 and debug your application. It sports configuration that enables an interactive debugger and settings optimized for development. Another :term:`PasteDeploy` ``.ini`` file named ``production.ini`` will also be created in the project directory. It sports configuration that disables any interactive debugger (to prevent inappropriate access and disclosure), and turns off a number of debugging settings. You can use this file to put your application into production, and you can modify it to do things like send email when an exception occurs. 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. .. 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 paster-generated project directory. The ``python`` you're invoking should be the one that lives in the ``bin`` directory of your virtual Python environment. Your terminal's current working directory *must* the the newly created project directory. For example: .. code-block:: text $ ../bin/python setup.py develop Elided output from a run of this command is shown below: .. code-block:: text $ ../bin/python setup.py develop ... Finished processing dependencies for MyProject==0.0 This will install a :term:`distribution` representing your project into the interpreter's library set so it can be found by ``import`` statements and by :term:`PasteDeploy` commands such as ``paster serve`` and ``paster pshell``. .. 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): .. code-block:: text $ ../bin/python setup.py test -q Here's sample output from a test run: .. code-block:: text $ 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 ``paster create`` -generated project. Within a project generated by the ``pyramid_starter`` template, a single sample test exists. .. index:: single: interactive shell single: IPython single: paster pshell .. _interactive_shell: The Interactive Shell --------------------- Once you've installed your program for development using ``setup.py develop``, you can use an interactive Python shell to examine your :app:`Pyramid` project's :term:`resource` and :term:`view` objects from a Python prompt. To do so, use your virtualenv's ``paster pshell`` command. The first argument to ``pshell`` is the path to your application's ``.ini`` file. The second is the ``app`` section name inside the ``.ini`` file which points to *your application* as opposed to any other section within the ``.ini`` file. For example, if your application ``.ini`` file might have a ``[app:MyProject]`` section that looks like so: .. code-block:: ini :linenos: [app:MyProject] use = egg:MyProject reload_templates = true debug_authorization = false debug_notfound = false debug_templates = true default_locale_name = en If so, you can use the following command to invoke a debug shell using the name ``MyProject`` as a section name: .. code-block:: text [chrism@vitaminf shellenv]$ ../bin/paster pshell development.ini MyProject Python 2.4.5 (#1, Aug 29 2008, 12:27:37) [GCC 4.0.1 (Apple Inc. build 5465)] on darwin Type "help" for more information. "root" is the Pyramid app root object, "registry" is the Pyramid registry object. >>> root >>> registry >>> registry.settings['debug_notfound'] False >>> from myproject.views import my_view >>> from pyramid.request import Request >>> r = Request.blank('/') >>> my_view(r) {'project': 'myproject'} Two names are made available to the pshell user as globals: ``root`` and ``registry``. ``root`` is the the object returned by the default :term:`root factory` in your application. ``registry`` is the :term:`application registry` object associated with your project's application (often accessed within view code as ``request.registry``). If you have `IPython `_ installed in the interpreter you use to invoke the ``paster`` command, the ``pshell`` command will use an IPython interactive shell instead of a standard Python interpreter shell. If you don't want this to happen, even if you have IPython installed, you can pass the ``--disable-ipython`` flag to the ``pshell`` command to use a standard Python interpreter shell unconditionally. .. code-block:: text [chrism@vitaminf shellenv]$ ../bin/paster pshell --disable-ipython \ development.ini MyProject You should always use a section name argument that refers to the actual ``app`` section within the Paste configuration file that points at your :app:`Pyramid` application *without any middleware wrapping*. In particular, a section name is inappropriate as the second argument to ``pshell`` if the configuration section it names is a ``pipeline`` rather than an ``app``. For example, if you have the following ``.ini`` file content: .. code-block:: ini :linenos: [app:MyProject] use = egg:MyProject reload_templates = true debug_authorization = false debug_notfound = false debug_templates = true default_locale_name = en [pipeline:main] pipeline = egg:WebError#evalerror MyProject Use ``MyProject`` instead of ``main`` as the section name argument to ``pshell`` against the above ``.ini`` file (e.g. ``paster pshell development.ini MyProject``). If you use ``main`` instead, an error will occur. Use the most specific reference to your application within the ``.ini`` file possible as the section name argument. Press ``Ctrl-D`` to exit the interactive shell (or ``Ctrl-Z`` on Windows). .. index:: single: running an application single: paster serve single: reload single: startup single: mod_wsgi Running The Project Application ------------------------------- Once a project is installed for development, you can run the application it represents using the ``paster serve`` command against the generated configuration file. In our case, this file is named ``development.ini``: .. code-block:: text $ ../bin/paster serve development.ini Here's sample output from a run of ``paster serve``: .. code-block:: text $ ../bin/paster serve development.ini Starting server in PID 16601. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543 By default, :app:`Pyramid` applications generated from a ``paster`` template will listen on TCP port 6543. You can shut down a server started this way by pressing ``Ctrl-C``. During development, it's often useful to run ``paster serve`` using its ``--reload`` option. When ``--reload`` is passed to ``paster serve``, 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: .. code-block:: text $ ../bin/paster serve development.ini --reload Starting subprocess with file monitor Starting server in PID 16601. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543 For more detailed information about the startup process, see :ref:`startup_chapter`. For more information about environment variables and configuration file settings that influence startup and runtime behavior, see :ref:`environment_chapter`. Viewing the Application ----------------------- Once your application is running via ``paster serve``, you may visit ``http://localhost:6543/`` in your browser. You will see something in your browser like what is displayed in the following image: .. image:: project.png This is the page shown by default when you visit an unmodified ``paster create`` -generated ``pyramid_starter`` application in a browser. .. sidebar:: Using an Alternate WSGI Server The code generated by :app:`Pyramid` ``paster`` templates assumes that you will be using the ``paster serve`` command to start your application while you do development. However, ``paster serve`` is by no means the only way to start up and serve a :app:`Pyramid` application. As we saw in :ref:`firstapp_chapter`, ``paster serve`` needn't be invoked at all to run a :app:`Pyramid` application. The use of ``paster serve`` to run a :app:`Pyramid` application is purely conventional based on the output of its ``paster`` templates. Any :term:`WSGI` server is capable of running a :app:`Pyramid` application. Some WSGI servers don't require the :term:`PasteDeploy` framework's ``paster serve`` command to do server process management at all. Each :term:`WSGI` server has its own documentation about how it creates a process to run an application, and there are many of them, so we cannot provide the details for each here. But the concepts are largely the same, whatever server you happen to use. One popular production alternative to a ``paster``-invoked server is :term:`mod_wsgi`. You can also use :term:`mod_wsgi` to serve your :app:`Pyramid` application using the Apache web server rather than any "pure-Python" server that is started as a result of ``paster serve``. See :ref:`modwsgi_tutorial` for details. However, it is usually easier to *develop* an application using a ``paster serve`` -invoked webserver, as exception and debugging output will be sent to the console. .. index:: single: project structure The Project Structure --------------------- The ``pyramid_starter`` template generated a :term:`project` (named ``MyProject``), which contains a Python :term:`package`. The package is *also* named ``myproject``, but it's lowercased; the paster template generates a project which contains a package that shares its name except for case. All :app:`Pyramid` ``paster`` -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 | |-- resources.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 ``paster serve``, as well as the deployment settings provided to that application. The generated ``development.ini`` file looks like so: .. latexbroken? .. literalinclude:: MyProject/development.ini :language: ini :linenos: This file contains several "sections" including ``[app:MyProject]``, ``[pipeline:main]``, and ``[server:main]``. The ``[app:MyProject]`` section represents configuration for your application. This section name represents the ``MyProject`` application (and it's an ``app`` -lication, thus ``app:MyProject``) The ``use`` setting is required in the ``[app:MyProject]`` section. The ``use`` setting points at a :term:`setuptools` :term:`entry point` named ``MyProject`` (the ``egg:`` prefix in ``egg:MyProject`` indicates that this is an entry point *URI* specifier, where the "scheme" is "egg"). ``egg:MyProject`` is actually shorthand for a longer spelling: ``egg:MyProject#main``. The ``#main`` part is omitted for brevity, as it is the default. .. sidebar:: ``setuptools`` Entry Points and PasteDeploy ``.ini`` Files This part of configuration can be confusing so let's try to clear things up a bit. Take a look at the generated ``setup.py`` file for this project. Note that the ``entry_point`` line in ``setup.py`` points at a string which looks a lot like an ``.ini`` file. This string representation of an ``.ini`` file has a section named ``[paste.app_factory]``. Within this section, there is a key named ``main`` (the entry point name) which has a value ``myproject:main``. The *key* ``main`` is what our ``egg:MyProject#main`` value of the ``use`` section in our config file is pointing at (although it is actually shortened to ``egg:MyProject`` there). The value represents a :term:`dotted Python name` path, which refers to a callable in our ``myproject`` package's ``__init__.py`` module. In English, this entry point can thus be referred to as a "Paste application factory in the ``MyProject`` project which has the entry point named ``main`` where the entry point refers to a ``main`` function in the ``mypackage`` module". If indeed if you open up the ``__init__.py`` module generated within the ``myproject`` package, you'll see a ``main`` function. This is the function called by :term:`PasteDeploy` when the ``paster serve`` command is invoked against our application. It accepts a global configuration object and *returns* an instance of our application. The ``use`` setting is the only setting *required* in the ``[app:MyProject]`` section unless you've changed the callable referred to by the ``egg:MyProject`` entry point to accept more arguments: other settings you add to this section are passed as keywords arguments to the callable represented by this entry point (``main`` in our ``__init__.py`` module). You can provide startup-time configuration parameters to your application by adding more settings to this section. The ``reload_templates`` setting in the ``[app:MyProject]`` 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 ``reload_templates`` option should be turned off for production applications, as template rendering is slowed when it is turned on. The ``debug_templates`` setting in the ``[app:MyProject]`` section is a :app:`Pyramid` -specific setting which is passed into the framework. If it exists, and its value is ``true``, :term:`Chameleon` template exceptions will contained more detailed and helpful information about the error than when this value is ``false``. See :ref:`debug_templates_section` for more information. .. warning:: The ``debug_templates`` option should be turned off for production applications, as template rendering is slowed when it is turned on. 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. ``[pipeline:main]``, has the name ``main`` signifying that this is the default 'application' (although it's actually a pipeline of middleware and an application) run by ``paster serve`` when it is invoked against this configuration file. The name ``main`` is a convention used by PasteDeploy signifying that it is the default application. 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``). The ``Paste#http`` server will create a new thread for each request. .. note:: In general, :app:`Pyramid` applications generated from paster templates should be threading-aware. It is not required that a :app:`Pyramid` application be nonblocking as all application code will run in its own thread, provided by the server you're using. 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. .. note:: You can add a ``[DEFAULT]`` section to your ``development.ini`` file. Such a section should consists of global parameters that are shared by all the applications, servers and :term:`middleware` defined within the configuration file. The values in a ``[DEFAULT]`` section will be passed to your application's ``main`` function as ``global_values``. ``production.ini`` ~~~~~~~~~~~~~~~~~~~ The ``development.ini`` file is a :term:`PasteDeploy` configuration file with a purpose much like that of ``development.ini``. However, it disables the WebError interactive debugger, replacing it with a logger which outputs exception messages to ``stderr`` by default. It also turns off template development options such that templates are not automatically reloaded when changed, and turns off all debugging options. You can use this file instead of ``development.ini`` when you put your application into production. .. 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 `_. 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, 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 use your application. .. warning:: 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 paster templates 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. ``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 Paste entry point. #. A ``resources.py`` module, which contains :term:`resource` code. #. 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 ``paster`` template: :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`` ~~~~~~~~~~~~~~~ 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. #. Line 2 imports the ``Root`` class from :mod:`myproject.resources` that we use later. #. Lines 4-12 define a function that returns a :app:`Pyramid` WSGI application. This function is meant to be called by the :term:`PasteDeploy` framework as a result of running ``paster serve``. Within this function, application configuration is performed. Lines 8-10 register a "default view" (a view that has no ``name`` attribute). It is registered so that it will be found when the :term:`context` of the request is an instance of the :class:`myproject.resources.Root` class. The first argument to ``add_view`` points at a Python function that does all the work for this view, also known as a :term:`view callable`, via a :term:`dotted Python name`. The view declaration also names a ``renderer``, which in this case is a template that will be used to render the result of the view callable. This particular view declaration points at ``myproject:templates/mytemplate.pt``, which is a :term:`asset specification` that specifies the ``mytemplate.pt`` file within the ``templates`` directory of the ``myproject`` package. The template file it actually points to is a :term:`Chameleon` ZPT template file. Line 11 registers a static view, which will serve up the files from the ``mypackage:static`` :term:`asset specification` (the ``static`` directory of the ``mypackage`` package). Line 12 returns a :term:`WSGI` application to the caller of the function (Paste). ``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: This bit of code was registered as the view callable within ``__init__.py`` (via ``add_view``). ``add_view`` said that the default URL for instances that are of the class :class:`myproject.resources.Root` should run this :func:`myproject.views.my_view` function. This view callable function is handed a single piece of information: the :term:`request`. The *request* is an instance of the :term:`WebOb` ``Request`` class representing the browser's request to our server. This view returns a dictionary. When this view is invoked, a :term:`renderer` converts the dictionary returned by the view into HTML, and returns the result as the :term:`response`. This view is configured to invoke a renderer which uses a :term:`Chameleon` ZPT template (``mypackage:templates/my_template.pt``, as specified in the ``__init__.py`` file call to ``add_view``). 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 ``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 ``reload_templates`` to ``false`` to increase the speed at which templates may be rendered. .. index:: single: resources.py .. _resourcespy_project_section: ``resources.py`` ~~~~~~~~~~~~~~~~ The ``resources.py`` module provides the :term:`resource` data and behavior for our application. Resources are objects which exist to provide site structure in applications which use :term:`traversal` to map URLs to code. We write a class named ``Root`` that provides the behavior for the root resource. .. literalinclude:: MyProject/myproject/resources.py :language: python :linenos: #. Lines 1-3 define the Root class. The Root class is a "root resource factory" function that will be called by the :app:`Pyramid` *Router* for each request when it wants to find the root of the resource tree. In a "real" application, the Root object would likely not be such a simple object. Instead, it might be an object that could access some persistent data store, such as a database. :app:`Pyramid` doesn't make any assumption about which sort of data storage you'll want to use, so the sample application uses an instance of :class:`myproject.resources.Root` to represent the root. ``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 exists in the project. Its contents are too long to show here, but it displays a default page when rendered. It is referenced by the call to ``add_view`` as the ``renderer`` attribute in the ``__init__`` 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. .. _modifying_package_structure: Modifying Package Structure ---------------------------- It is best practice for your application's code layout to not stray too much from accepted Pyramid paster template 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 paster template are in no way magical or required. Despite the choices made for you by any paster template, 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 ``pyramid_starter`` paster template 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 ``mypackage`` 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*. Then change the __init__.py of your myproject project (*not* the ``__init__.py`` you just created in the ``views`` directory, the one in its parent directory). For example, from something like: .. code-block:: python :linenos: config.add_view('myproject.views.my_view', renderer='myproject:templates/mytemplate.pt') To this: .. code-block:: python :linenos: config.add_view('myproject.views.blog.my_view', renderer='myproject:templates/mytemplate.pt') You can then continue to add files to the ``views`` directory, and refer to view classes or functions within those files via the dotted name passed as the first argument to ``add_view``. For example, if you added a file named ``anothermodule.py`` to the ``views`` subdirectory, and added a view callable named ``my_view`` to it: .. code-block:: python :linenos: config.add_view('myproject.views.anothermodule.my_view', renderer='myproject:templates/anothertemplate.pt') This pattern can be used to rearrage code referred to by any Pyramid API argument which accepts a :term:`dotted Python name` or direct object reference.