.. _project_narr: Creating a :mod:`repoze.bfg` Project ==================================== You can use :mod:`repoze.bfg` 's sample application generator to get started. This generator uses :term:`Paste` templates to allow creation of a new project by answering a series of questions. Creating the Project -------------------- To start a :mod:`repoze.bfg` :term:`project`, use the ``paster create`` facility using the interpreter from the virtualenv (``bfgenv``) directory you created in :ref:`installing_chapter`. .. code-block:: bash :linenos: $ bin/paster create -t bfg_starter ``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:: bash :linenos: $ bin/paster create -t bfg_starter Selected and implied templates: repoze.bfg#bfg repoze.bfg starter project Enter project name: MyProject Variables: egg: MyProject package: myproject project: MyProject Creating template bfg Creating directory ./MyProject Recursing into +package+ Creating ./MyProject/myproject/ Copying __init__.py to ./MyProject/myproject/__init__.py Copying configure.zcml to ./MyProject/myproject/configure.zcml Copying models.py to ./MyProject/myproject/models.py Copying run.py_tmpl to ./MyProject/myproject/run.py Recursing into templates Creating ./MyProject/myproject/templates/ Copying mytemplate.pt to ./MyProject/myproject/templates/mytemplate.pt Recursing into static Creating ./MyProject/myproject/templates/static/ Copying default.css to ./MyProject/myproject/templates/static/default.css Recursing into images Creating ./MyProject/myproject/templates/static/images/ Copying img01.gif to ./MyProject/myproject/templates/static/images/img01.gif Copying img02.gif to ./MyProject/myproject/templates/static/images/img02.gif Copying img03.gif to ./MyProject/myproject/templates/static/images/img03.gif Copying img04.gif to ./MyProject/myproject/templates/static/images/img04.gif Copying spacer.gif to ./MyProject/myproject/templates/static/images/spacer.gif Copying templatelicense.txt to ./MyProject/myproject/templates/static/templatelicense.txt Copying tests.py_tmpl to ./MyProject/myproject/tests.py Copying views.py_tmpl to ./MyProject/myproject/views.py Copying +project+.ini_tmpl to ./MyProject/MyProject.ini Copying CHANGES.txt_tmpl to ./MyProject/CHANGES.txt Copying README.txt_tmpl to ./MyProject/README.txt Copying ez_setup.py to ./MyProject/ez_setup.py Copying setup.py_tmpl to ./MyProject/setup.py Running /Users/chrism/projects/repoze/bfg/bin/python setup.py egg_info As a result of the above, a project is created in a directory named ``MyProject``. That directory is a :term:`setuptools` :term:`project` directory from which a Python setuptools :term:`distribution` can be created. The ``setup.py`` file in that directory can be used to distribute your application, or install your application for deployment or development. A sample :term:`PasteDeploy` ``.ini`` file named ``MyProject.ini`` will also be created in the project directory. You will use the ``paster serve`` command against this ``.ini`` file to run your application. The ``MyProject`` project directory contains an additional subdirectory named ``myproject`` (note the case difference) representing a Python :term:`package` which holds very simple :mod:`repoze.bfg` sample code. This is where you'll edit your application's Python code and templates. .. 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 bfg_starter MyProject``. .. note:: Convenience :term:`Paste` templates for projects which will depend on :term:`ZODB` or `SQLAlchemy `_ also exist. Use ``paster create -t bfg_zodb`` to create a project that depends on ZODB. Use ``paster create -t bfg_routesalchemy`` to create a project that depends on SQLAlchemy and Routes (uses :term:`URL dispatch` instead of :term:`traversal`). Use ``paster create -t bfg_alchemy`` to create a project that depends on SQLAlchemy but *not* Routes (uses :term:`traversal` instead of :term:`URL dispatch`). Installing your Newly Created Project for Development ----------------------------------------------------- Using the interpreter from the :term:`virtualenv` you create during :ref:`installing_chapter`, invoke the following command when inside the project directory against the generated ``setup.py``: .. code-block:: bash :linenos: $ ../bin/python setup.py develop Elided output from a run of this command is shown below: .. code-block:: bash :linenos: $ ../bin/python setup.py develop ... Finished processing dependencies for MyProject==0.1 This will install your application's :term:`package` into the interpreter so it can be found and run as a :term:`WSGI` application inside a WSGI server. Running The Tests For Your Application -------------------------------------- To run unit tests for your application, you should invoke them like so: .. code-block:: bash :linenos: $ ../bin/python setup.py test -q Here's sample output from a test run: .. code-block:: bash :linenos: $ 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 2 tests in 0.647s OK The tests are found in the ``tests.py`` module in your ``paster create`` -generated project. Two sample tests exist. The Interactive Shell --------------------- Once you've installed your program for development using ``setup.py develop``, you can use an interactive shell to examine your BFG application from a Python prompt. To do so, use the ``paster`` shell command with the ``bfgshell`` argument: The first argument to ``bfgshell`` is the path to your application's ``.ini`` file. The second is the section name inside the ``.ini`` file which points to your application. .. code-block:: bash :linenos: [chrism@vitaminf bfgshellenv]$ ../bin/paster bfgshell MyProject.ini main 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 BFG app root object. >>> root If that command fails because ``paster`` claims it knows nothing about the "bfgshell" command (this happens under certain conditions that are not yet well-understood) try passing the flag ``--plugin=repoze.bfg`` before the filename: .. code-block:: bash :linenos: [chrism@vitaminf bfgshellenv]$ ../bin/paster --plugin=repoze.bfg bfgshell MyProject.ini main Press Ctrl-D to exit the interactive shell. You should always use a section name argument that refers to the actual ``app`` section within the config file that points at your BFG application *without any middleware wrapping*. In particular, a section name is inappropriate as the second argument to "bfgshell" if the configuration section it names is a ``pipeline`` rather than an ``app``. Runnning The Project Application -------------------------------- Once the project is installed for development, you can run the application it represents using the ``paster serve`` command against the generated ``MyProject.ini`` configuration file: .. code-block:: bash :linenos: $ ../bin/paster serve MyProject.ini Here's sample output from a run: .. code-block:: bash :linenos: $ paster serve MyProject.ini Starting server in PID 16601. serving on 0.0.0.0:6543 view at http://127.0.0.1:6543 By default, generated :mod:`repoze.bfg` applications will listen on port 6543. .. note:: During development, it's often useful to run ``paster serve`` using its ``--reload`` option. When any Python module your project uses, changes, it will restart the server, which makes development easier, as changes to Python code under :mod:`repoze.bfg` is not put into effect until the server restarts. Viewing the Application ----------------------- Visit ``http://localhost:6543/`` in your browser. You will see something in your browser like what is displayed below: .. image:: project.png That's the page shown by default when you visit an unmodified ``paster create``-generated application. The Project Structure --------------------- Our generated :mod:`repoze.bfg` application is a setuptools :term:`project` (named ``MyProject``), which contains a Python :term:`package` (which is *also* named ``myproject``, but lowercased; the paster template generates a project which contains a package that shares its name except for case). The ``MyProject`` project has the following directory structure:: MyProject/ |-- CHANGES.txt |-- README.txt |-- ez_setup.py |-- myproject | |-- __init__.py | |-- configure.zcml | |-- models.py | |-- run.py | |-- templates | | |-- mytemplate.pt | | `-- static/ | |-- tests.py | `-- views.py |-- MyProject.ini `-- setup.py The ``MyProject`` :term:`Project` --------------------------------- The ``MyProject`` :term:`project` 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. #. ``ez_setup.py`` is a file that is used by ``setup.py`` to install :term:`Setuptools` if the executing user does not have it installed. #. ``MyProject.ini`` is a :term:`PasteDeploy` configuration file that can be used to execute your application. #. ``setup.py`` is the file you'll use to test and distribute your application. It is a standard :term:`setuptools` ``setup.py`` file. We won't describe the ``CHANGES.txt`` or ``README.txt`` files. ``ez_setup.py`` is a file only used by ``setup.py`` in case a user who wants to install your package does not have :term:`Setuptools` already installed. It is only imported by and used by ``setup.py``, so we won't describe it here. .. _MyProject_ini: ``MyProject.ini`` ~~~~~~~~~~~~~~~~~ The ``MyProject.ini`` file is a :term:`PasteDeploy` configuration file. Its purpose is to specify an application to run when you invoke ``paster serve`` when you start an application, as well as the options provided to that application. The generated ``MyProject.ini`` file looks like so: .. literalinclude:: MyProject/MyProject.ini :linenos: This file contains several "sections" including ``[DEFAULT]``, ``[app:main]``, and ``[server:main]``. The ``[DEFAULT]`` section consists of global parameters that are shared by all the applications, servers and :term:`middleware` defined within the configuration file. By default it contains one key ``debug``, which is set to ``true``. This key is used by various components to decide whether to act in a "debugging" mode. ``repoze.bfg`` itself does not do anything with this parameter as of this writing, and neither does the generated sample application. The ``[app:main]`` section represents configuration for your application. This section name represents the ``main`` application (and it's an ``app`` -lication, thus ``app:main``), sigifiying that this is the default application run by ``paster serve`` when it is invoked against this configuration file. The name ``main`` is a convention signifying that it the default application. The ``use`` setting is required in the ``[app:main]`` section. The ``use`` setting points at a :term:`setuptools` :term:`entry point` named ``MyProject#app`` (the ``egg:`` prefix in ``egg:MyProject#app`` indicates that this is an entry point *URI* specifier, where the "scheme" is "egg"; there are no other schemes currently, so the ``egg:`` prefix is arguably not very useful). .. note:: 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 ``app`` (the entry point name) which has a value ``myproject.run:app``. The *key* ``app`` is what our ``egg:MyProject#app`` value of the ``use`` section in our config file is pointing at. The value represents a Python "dotted-name" path, which refers to a callable in our ``myproject`` package's ``run.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 ``app`` where the entry point refers to a ``app`` function in the ``mypackage.run`` module". If indeed if you open up the ``run.py`` module generated within the ``myproject`` package, you'll see a ``app`` function. This is the function called :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:main]`` section unless you've changed the callable referred to by the ``MyProject#app`` 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 (``app`` in our ``run.py`` module). You can provide startup-time configuration parameters to your application by requiring more settings in this section. The ``reload_templates`` setting in the ``[app:main]`` section is a :mod:`repoze.bfg`-specific setting which is passed into the framework. If it exists, and is ``true``, :term:`Chameleon` 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. Various other settings may exist in this section having to do with debugging a :mod:`repoze.bfg` application. See :ref:`environment_chapter` for more information about these settings. The ``[server:main]`` section of the configuration file configures a WSGI server which listens on 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, ``repoze.bfg`` applications should be threading-aware. It is not required that a ``repoze.bfg`` 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 servers. ``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 :term:`Setuptools` documentation. Our generated ``setup.py`` looks like this: .. literalinclude:: MyProject/setup.py :linenos: The top of the file imports and uses ``ez_setup``, which causes :term:`Setuptools` to be installed on an invoking user's computer if it isn't already. 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 explan everything about setuptools setup files, we'll provide a whirlwind tour of what exists in this file here. Your application's name (this can be any string) 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 ship as a zipped egg (it will unpack as a directory, which is more convenient). ``install_requires`` and ``tests_require`` indicate that this package depends on the ``repoze.bfg`` package. ``test_suite`` points at the package for our application, which means all tests found in the package will be installed. We examined ``entry_points`` in our discussion of the ``MyProject.ini`` file; this file defines the ``app`` entry point that represent's 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:: 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:: By default, ``setup.py sdist`` does not place non-Python-source files in generated tarballs. This means, in this case, that the ``templates/mytemplate.pt`` file and the files in the ``templates/static`` directory are not packaged in the 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 a version control system such as 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. The ``myproject`` :term:`Package` --------------------------------- The ``myproject`` :term:`package` lives inside the ``MyProject`` :term:`project`. It contains: #. An ``__init__.py`` file which signifies that this is a Python :term:`package`. It is conventionally empty, save for a single comment at the top. #. A ``configure.zcml`` is a :term:`ZCML` file which maps view names to model types. This is also known as the :term:`application registry`. #. A ``models.py`` module, which contains :term:`model` code. #. A ``run.py`` module, which contains code that helps users run the application. #. 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: :mod:`repoze.bfg` doesn't insist that you name things in any particular way. ``configure.zcml`` ~~~~~~~~~~~~~~~~~~ The ``configure.zcml`` represents the :term:`application registry`. It looks like so: .. literalinclude:: MyProject/myproject/configure.zcml :linenos: :language: xml #. Lines 1 provides the root node and namespaces for the configuration language. ``http://namespaces.repoze.org/bfg`` is the default XML namespace. Add-on packages may require other namespaces. #. Lines 4 initializes :mod:`repoze.bfg`-specific configuration directives by including the ``repoze.bfg.includes`` package. This causes all of the ZCML within the ``configure.zcml`` of the ``repoze.bfg.includes`` package (which can be found in the main :mod:`repoze.bfg` sources). #. Lines 6-9 register a "default view" (a view that has no ``name`` attribute). It is ``for`` model objects that are instances of the ``MyModel`` class. The ``view`` attribute points at a Python function that does all the work for this view. Note that the values of both the ``for`` attribute and the ``view`` attribute begin with a single period. Names that begin with a period are "shortcuts" which point at files relative to the :term:`package` in which the ``configure.zcml`` file lives. In this case, since the ``configure.zcml`` file lives within the ``myproject`` package, the shorcut ``.models.MyModel`` could also be spelled ``myproject.models.MyModel`` (forming a full Python dotted-path name to the ``MyModel`` class). Likewise the shortcut ``.views.my_view`` could be replaced with ``myproject.views.my_view``. #. Lines 11-15 register a view named ``static``. This view declaration points at the ``static_view``, which is a view implementation that serves static files from the filesystem for the default application. ``views.py`` ~~~~~~~~~~~~ Much of the heavy lifting in a :mod:`repoze.bfg` application comes in the form of *views*. A :term:`view` is the bridge between the content in the model, and the HTML given back to the browser. .. literalinclude:: MyProject/myproject/views.py :linenos: #. Lines 1-2 import required functions. #. Line 4 sets up a ``static_view`` which will be consulted when visitors visit ``/static/``. This view will serve up CSS and images in our default application. This view is registered in ``configure.zcml`` as the ``static`` view name for the class ``MyModel`` (the root). #. Lines 6-9 provide the ``my_view`` that was registered as the view. ``configure.zcml`` said that the default URL for instances that are of the class ``MyModel`` should run this ``my_view`` function. The function is handed two pieces of information: the :term:`context` and the term:`request`. The *context* is the term :term:`model` found via :term:`traversal` (or via :term:`URL dispatch`). The *request* is an instance of the :term:`WebOb` ``Request`` class representing the browser's request to our server. #. The view renders a :term:`Chameleon` template and returns the result as the :term:`response`. Note that because our ``MyProject.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. .. note:: This example uses ``render_template_to_response`` which is a shortcut function. If you want more control over the response, use the ``render_template`` function, also present in :ref:`template_module`. You may then create your own :term:`WebOb` Response object, using the result of ``render_template`` as the response's body. There is also a ``get_template`` API in the same module, which you can use to retrieve the template object without rendering it at all, for additional control. .. note:: For more information about the ``static`` view helper function see :ref:`static_resources_section`. .. _modelspy_project_section: ``models.py`` ~~~~~~~~~~~~~ The ``models.py`` module provides the :term:`model` data for our application. We write a class named ``MyModel`` that provides the behavior. .. literalinclude:: MyProject/myproject/models.py :linenos: #. Lines 1-2 define the MyModel class. #. Line 4 defines an instance of MyModel as the root. #. Line 6 is a "root factory" function that will be called by the :mod:`repoze.bfg` *Router* for each request when it wants to find the root of the model graph. Conventionally this is called ``get_root``. In a "real" application, the root object would not be such a simple object. Instead, it would be an object that could access some persistent data store, such as a database. :mod:`repoze.bfg` doesn't make any assumption about which sort of datastore you'll want to use, so the sample application uses an instance of ``MyModel`` to represent the root. ``run.py`` ~~~~~~~~~~ We need a small Python module that configures our application and advertises itself to our :term:`PasteDeploy` ``.ini`` file. For convenience, we also make it possible to run this module directory without the PasteDeploy configuration file: .. literalinclude:: MyProject/myproject/run.py :linenos: #. Line 1 imports the ``make_app`` functions from :mod:`repoze.bfg.router` that we use later. #. Lines 3-10 define a function that returns a :mod:`repoze.bfg` Router application from :ref:`router_module` . This is meant to be called by the :term:`PasteDeploy` framework as a result of running ``paster serve``. ``templates/mytemplate.pt`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~ The single :term:`Chameleon` template in the project looks like so: .. literalinclude:: MyProject/myproject/templates/mytemplate.pt :linenos: :language: xml It displays a default page when rendered. It is referenced by the ``my_view`` function in the ``views.py`` module. Templates are accessed and used by view functions. ``templates/static`` ~~~~~~~~~~~~~~~~~~~~ This directory contains static resources which support the ``mytemplate.pt`` template. It includes CSS and images. ``tests.py`` ~~~~~~~~~~~~ The ``tests.py`` module includes unit tests for your application. .. literalinclude:: MyProject/myproject/tests.py :linenos: This sample ``tests.py`` file has a single unit test and a single integration test defined within it. These two tests are executed when you run ``setup.py test -q``. You may add more tests here as you build your application. You are not required to write tests to use :mod:`repoze.bfg`, this file is simply provided as convenience and example.