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diff --git a/docs/narr/introduction.rst b/docs/narr/introduction.rst index a37d74c9b..dada4e8bd 100644 --- a/docs/narr/introduction.rst +++ b/docs/narr/introduction.rst @@ -7,905 +7,356 @@ single: framework :app:`Pyramid` Introduction -============================== - -:app:`Pyramid` is a general, open source, Python web application development -*framework*. Its primary goal is to make it easier for a Python developer to -create web applications. - -.. sidebar:: Frameworks vs. Libraries - - A *framework* differs from a *library* in one very important way: - library code is always *called* by code that you write, while a - framework always *calls* code that you write. Using a set of - libraries to create an application is usually easier than using a - framework initially, because you can choose to cede control to - library code you have not authored very selectively. But when you - use a framework, you are required to cede a greater portion of - control to code you have not authored: code that resides in the - framework itself. You needn't use a framework at all to create a - web application using Python. A rich set of libraries already - exists for the platform. In practice, however, using a framework - to create an application is often more practical than rolling your - own via a set of libraries if the framework provides a set of - facilities that fits your application requirements. - -Pyramid attempts to follow these design and engineering principles: +=========================== + +:app:`Pyramid` is a Python web application *framework*. It is designed to make creating web applications easier. It is open source. + +.. sidebar:: What Is a Framework? + + A *framework* provides capabilities that developers can enhance or extend. A web application framework provides many of the common needs of building web applications allowing developers to concentrate only on the parts that are specific to their application. + + Every framework makes choices about how a particular problem should be solved. When developers choose to use a framework, they cede control over the portions of their application that are provided by the framework. It is possible to write a complete web application without any framework, by using Python libraries. In practice, however, it is often more practical to use a framework, so long as your chosen framework fits the requirements of your application. + +:app:`Pyramid` follows these design and engineering principles: Simplicity - :app:`Pyramid` takes a *"pay only for what you eat"* approach. You can get - results even if you have only a partial understanding of :app:`Pyramid`. - It doesn’t force you to use any particular technology to produce an - application, and we try to keep the core set of concepts that you need to - understand to a minimum. + :app:`Pyramid` is designed to be easy to use. You can get started even if you don't understand it all. And when you're ready to do more, :app:`Pyramid` will be there for you. Minimalism - :app:`Pyramid` tries to solve only the fundamental problems of creating - a web application: the mapping of URLs to code, templating, security and - serving static assets. We consider these to be the core activities that are - common to nearly all web applications. + Out of the box, :app:`Pyramid` provides only the core tools needed for nearly all web applications: mapping URLs to code, security, and serving static assets (files like JavaScript and CSS). Additional tools provide templating, database integration and more. But with :app:`Pyramid` you can *"pay only for what you eat"*. Documentation - Pyramid's minimalism means that it is easier for us to maintain complete - and up-to-date documentation. It is our goal that no aspect of Pyramid - is undocumented. + :app:`Pyramid` is committed to comprehensive and up-to-date documentation. Speed - :app:`Pyramid` is designed to provide noticeably fast execution for common - tasks such as templating and simple response generation. + :app:`Pyramid` is designed to be noticeably fast. Reliability - :app:`Pyramid` is developed conservatively and tested exhaustively. Where - Pyramid source code is concerned, our motto is: "If it ain’t tested, it’s - broke". + :app:`Pyramid` is developed conservatively and tested exhaustively. Our motto is: "If it ain't tested, it's broke". Openness - As with Python, the Pyramid software is distributed under a `permissive - open source license <http://repoze.org/license.html>`_. + As with Python, the :app:`Pyramid` software is distributed under a `permissive open source license <http://repoze.org/license.html>`_. -.. _what_makes_pyramid_unique: +.. _why_pyramid: -What Makes Pyramid Unique -------------------------- - -Understandably, people don't usually want to hear about squishy engineering -principles, they want to hear about concrete stuff that solves their -problems. With that in mind, what would make someone want to use Pyramid -instead of one of the many other web frameworks available today? What makes -Pyramid unique? - -This is a hard question to answer, because there are lots of excellent -choices, and it's actually quite hard to make a wrong choice, particularly in -the Python web framework market. But one reasonable answer is this: you can -write very small applications in Pyramid without needing to know a lot. -"What?", you say, "that can't possibly be a unique feature, lots of other web -frameworks let you do that!" Well, you're right. But unlike many other -systems, you can also write very large applications in Pyramid if you learn a -little more about it. Pyramid will allow you to become productive quickly, -and will grow with you; it won't hold you back when your application is small -and it won't get in your way when your application becomes large. "Well -that's fine," you say, "lots of other frameworks let me write large apps -too." Absolutely. But other Python web frameworks don't seamlessly let you -do both. They seem to fall into two non-overlapping categories: frameworks -for "small apps" and frameworks for "big apps". The "small app" frameworks -typically sacrifice "big app" features, and vice versa. - -We don't think it's a universally reasonable suggestion to write "small apps" -in a "small framework" and "big apps" in a "big framework". You can't really -know to what size every application will eventually grow. We don't really -want to have to rewrite a previously small application in another framework -when it gets "too big". We believe the current binary distinction between -frameworks for small and large applications is just false; a well-designed -framework should be able to be good at both. Pyramid strives to be that kind -of framework. - -To this end, Pyramid provides a set of features that, combined, are unique -amongst Python web frameworks. Lots of other frameworks contain some -combination of these features; Pyramid of course actually stole many of them -from those other frameworks. But Pyramid is the only one that has all of -them in one place, documented appropriately, and useful a la carte without -necessarily paying for the entire banquet. These are detailed below. - -Single-file applications -~~~~~~~~~~~~~~~~~~~~~~~~ - -You can write a Pyramid application that lives entirely in one Python file, -not unlike existing Python microframeworks. This is beneficial for one-off -prototyping, bug reproduction, and very small applications. These -applications are easy to understand because all the information about the -application lives in a single place, and you can deploy them without needing -to understand much about Python distributions and packaging. Pyramid isn't -really marketed as a microframework, but it allows you to do almost -everything that frameworks that are marketed as micro offer in very similar -ways. +Why Pyramid? +------------ -.. literalinclude:: helloworld.py - -.. seealso:: +In a world filled with web frameworks, why should you choose :app:`Pyramid`\ ? - See also :ref:`firstapp_chapter`. - -Decorator-based configuration -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -If you like the idea of framework configuration statements living next to the -code it configures, so you don't have to constantly switch between files to -refer to framework configuration when adding new code, you can use Pyramid -decorators to localize the configuration. For example: - -.. code-block:: python +Modern +~~~~~~ - from pyramid.view import view_config - from pyramid.response import Response +:app:`Pyramid` is fully compatible with Python 3. If you develop a :app:`Pyramid` application today, you can rest assured that you'll be able to use the most modern features of your favorite language. And in the years to come, you'll continue to bed working on a framework that is up-to-date and forward-looking. - @view_config(route_name='fred') - def fred_view(request): - return Response('fred') +Tested +~~~~~~ -However, unlike some other systems, using decorators for Pyramid -configuration does not make your application difficult to extend, test or -reuse. The :class:`~pyramid.view.view_config` decorator, for example, does -not actually *change* the input or output of the function it decorates, so -testing it is a "WYSIWYG" operation; you don't need to understand the -framework to test your own code, you just behave as if the decorator is not -there. You can also instruct Pyramid to ignore some decorators, or use -completely imperative configuration instead of decorators to add views. -Pyramid decorators are inert instead of eager: you detect and activate them -with a :term:`scan`. +Untested code is broken by design. The :app:`Pyramid` community has a strong testing culture and our framework reflects that. Every release of :app:`Pyramid` has 100% statement coverage (as measured by `coverage <https://coverage.readthedocs.io/en/latest/>`_) and 95% decision/condition coverage. (as measured by `instrumental <https://instrumental.readthedocs.io/en/latest/intro.html>`_) It is automatically tested using `Travis <https://travis-ci.org/Pylons/pyramid>`_ and `Jenkins <http://jenkins.pylonsproject.org/job/pyramid/>`_ on supported versions of Python after each commit to its GitHub repository. `Official Pyramid add-ons <https://trypyramid.com/extending-pyramid.html>`_ are held to a similar testing standard. -Example: :ref:`mapping_views_using_a_decorator_section`. +We still find bugs in :app:`Pyramid`, but we've noticed we find a lot fewer of them while working on projects with a solid testing regime. -URL generation -~~~~~~~~~~~~~~ +Documented +~~~~~~~~~~ -Pyramid is capable of generating URLs for resources, routes, and static -assets. Its URL generation APIs are easy to use and flexible. If you use -Pyramid's various APIs for generating URLs, you can change your configuration -around arbitrarily without fear of breaking a link on one of your web pages. +The :app:`Pyramid` documentation is comprehensive. We strive to keep our narrative documentation both complete and friendly to newcomers. We also maintain the :ref:`Pyramid Community Cookbook <cookbook:pyramid-cookbook>` of recipes demonstrating common scenarios you might face. Contributions in the form of improvements to our documentation are always appreciated. And we always welcome improvements to our :ref:`official tutorials <html_tutorials>` as well as new contributions to our :ref:`community maintained tutorials <tutorials:pyramid-tutorials>`. -Example: :ref:`generating_route_urls`. +Supported +~~~~~~~~~ -Static file serving -~~~~~~~~~~~~~~~~~~~ +You can get help quickly with :app:`Pyramid`. It's our goal that no :app:`Pyramid` question go unanswered. Whether you ask a question on IRC, on the Pylons-discuss mailing list, or on StackOverflow, you're likely to get a reasonably prompt response. -Pyramid is perfectly willing to serve static files itself. It won't make you -use some external web server to do that. You can even serve more than one -set of static files in a single Pyramid web application (e.g. ``/static`` and -``/static2``). You can also, optionally, place your files on an external web -server and ask Pyramid to help you generate URLs to those files, so you can -use Pyramid's internal fileserving while doing development, and a faster -static file server in production without changing any code. +:app:`Pyramid` is also a welcoming, friendly space for newcomers. We don't tolerate "support trolls" or those who enjoy berating fellow users in our support channels. We try to keep it well-lit and new-user-friendly. -Example: :ref:`static_assets_section`. +.. seealso:: -Fully Interactive Development -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + See also our `#pyramid IRC channel <https://webchat.freenode.net/?channels=pyramid>`_, our `pylons-discuss mailing list <https://groups.google.com/forum/#!forum/pylons-discuss>`_, and :ref:`support-and-development`. -When developing a Pyramid application, several interactive features are -available. Pyramid can automatically utilize changed templates when rendering -pages and automatically restart the application to incorporate changed python -code. Plain old ``print()`` calls used for debugging can display to a console. +.. _what_makes_pyramid_unique: -Pyramid's debug toolbar comes activated when you use a Pyramid scaffold to -render a project. This toolbar overlays your application in the browser, and -allows you access to framework data such as the routes configured, the last -renderings performed, the current set of packages installed, SQLAlchemy -queries run, logging data, and various other facts. When an exception -occurs, you can use its interactive debugger to poke around right in your -browser to try to determine the cause of the exception. It's handy. +What makes Pyramid unique +------------------------- -Example: :ref:`debug_toolbar`. +There are many tools available for web development. What would make someone want to use :app:`Pyramid` instead? What makes :app:`Pyramid` unique? -Debugging settings -~~~~~~~~~~~~~~~~~~ +With :app:`Pyramid` you can write very small applications without needing to know a lot. And by learning a bit more, you can write very large applications too. :app:`Pyramid` will allow you to become productive quickly, and will grow with you. It won't hold you back when your application is small, and it won't get in your way when your application becomes large. Other application frameworks seem to fall into two non-overlapping categories: those that support "small apps" and those designed for "big apps". -Pyramid has debugging settings that allow you to print Pyramid runtime -information to the console when things aren't behaving as you're expecting. -For example, you can turn on "debug_notfound", which prints an informative -message to the console every time a URL does not match any view. You can -turn on "debug_authorization", which lets you know why a view execution was -allowed or denied by printing a message to the console. These features are -useful for those WTF moments. +We don't believe you should have to make this choice. You can't really know how large your application will become. You certainly shouldn't have to rewrite a small application in another framework when it gets "too big". A well-designed framework should be able to be good at both. :app:`Pyramid` is that kind of framework. -There are also a number of commands that you can invoke within a Pyramid -environment that allow you to introspect the configuration of your system: -``proutes`` shows all configured routes for an application in the order -they'll be evaluated for matching; ``pviews`` shows all configured views for -any given URL. These are also WTF-crushers in some circumstances. +:app:`Pyramid` provides a set of features that are unique among Python web frameworks. Others may provide some, but only :app:`Pyramid` provides them all, in one place, fully documented, and *à la carte* without needing to pay for the whole banquet. -Examples: :ref:`debug_authorization_section` and :ref:`command_line_chapter`. -Add-ons -~~~~~~~~ +Build single-file applications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Pyramid has an extensive set of add-ons held to the same quality standards as -the Pyramid core itself. Add-ons are packages which provide functionality -that the Pyramid core doesn't. Add-on packages already exist which let you -easily send email, let you use the Jinja2 templating system, let you use -XML-RPC or JSON-RPC, let you integrate with jQuery Mobile, etc. +You can write a :app:`Pyramid` application that lives entirely in one Python file. Such an application is easy to understand since everything is in one place. It is easy to deploy because you don't need to know much about Python packaging. :app:`Pyramid` allows you to do almost everything that so-called *microframeworks* can in very similar ways. -Examples: http://docs.pylonsproject.org/en/latest/docs/pyramid.html#pyramid-add-on-documentation +.. literalinclude:: helloworld.py +.. seealso:: -Class-based and function-based views -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + See also :ref:`firstapp_chapter`. -Pyramid has a structured, unified concept of a :term:`view callable`. -View callables can be functions, methods of classes, or even instances. When -you add a new view callable, you can choose to make it a function or a method -of a class; in either case, Pyramid treats it largely the same way. You can -change your mind later, and move code between methods of classes and -functions. A collection of similar view callables can be attached to a -single class as methods, if that floats your boat, and they can share -initialization code as necessary. All kinds of views are easy to understand -and use and operate similarly. There is no phony distinction between them; -they can be used for the same purposes. +Configure applications with decorators +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Here's a view callable defined as a function: +:app:`Pyramid` allows you to keep your configuration right next to your code. That way you don't have to switch files to see your configuration. For example: .. code-block:: python - :linenos: - from pyramid.response import Response - from pyramid.view import view_config + from pyramid.view import view_config + from pyramid.response import Response - @view_config(route_name='aview') - def aview(request): - return Response('one') + @view_config(route_name='fred') + def fred_view(request): + return Response('fred') -Here's a few views defined as methods of a class instead: +However, using :app:`Pyramid` configuration decorators does not change your code. It remains easy to extend, test, or reuse. You can test your code as if the decorators were not there. You can instruct the framework to ignore some decorators. You can even use an imperative style to write your configuration, skipping decorators entirely. -.. code-block:: python - :linenos: - - from pyramid.response import Response - from pyramid.view import view_config +.. seealso:: - class AView(object): - def __init__(self, request): - self.request = request + See also :ref:`mapping_views_using_a_decorator_section`. - @view_config(route_name='view_one') - def view_one(self): - return Response('one') +Generate application URLs +~~~~~~~~~~~~~~~~~~~~~~~~~ - @view_config(route_name='view_two') - def view_two(self): - return Response('two') +Dynamic web applications produce URLs that can change depending on what you are viewing. :app:`Pyramid` provides flexible, consistent, easy to use tools for generating URLs. When you use these tools to write your application, you can change your configuration without fear of breaking links in your web pages. .. seealso:: - See also :ref:`view_config_placement`. + See also :ref:`generating_route_urls`. -.. _intro_asset_specs: +Serve static assets +~~~~~~~~~~~~~~~~~~~ -Asset specifications -~~~~~~~~~~~~~~~~~~~~ +Web applications often require JavaScript, CSS, images and other so-called *static assets*. :app:`Pyramid` provides flexible tools for serving these kinds of files. You can serve them directly from :app:`Pyramid`, or host them on an external server or CDN (content delivery network). Either way, :app:`Pyramid` can help you to generate URLs so you can change where your files come from without changing any code. -Asset specifications are strings that contain both a Python package name and -a file or directory name, e.g. ``MyPackage:static/index.html``. Use of these -specifications is omnipresent in Pyramid. An asset specification can refer -to a template, a translation directory, or any other package-bound static -resource. This makes a system built on Pyramid extensible, because you don't -have to rely on globals ("*the* static directory") or lookup schemes ("*the* -ordered set of template directories") to address your files. You can move -files around as necessary, and include other packages that may not share your -system's templates or static files without encountering conflicts. - -Because asset specifications are used heavily in Pyramid, we've also provided -a way to allow users to override assets. Say you love a system that someone -else has created with Pyramid but you just need to change "that one template" -to make it all better. No need to fork the application. Just override the -asset specification for that template with your own inside a wrapper, and -you're good to go. +.. seealso:: -Examples: :ref:`asset_specifications` and :ref:`overriding_assets_section`. + See also :ref:`static_assets_section`. -Extensible templating +Develop interactively ~~~~~~~~~~~~~~~~~~~~~ -Pyramid has a structured API that allows for pluggability of "renderers". -Templating systems such as Mako, Genshi, Chameleon, and Jinja2 can be treated -as renderers. Renderer bindings for all of these templating systems already -exist for use in Pyramid. But if you'd rather use another, it's not a big -deal. Just copy the code from an existing renderer package, and plug in your -favorite templating system. You'll then be able to use that templating -system from within Pyramid just as you'd use one of the "built-in" templating -systems. +:app:`Pyramid` can automatically detect changes you make to template files and code, so your changes are immediately available in your browser. You can debug using plain old ``print()`` calls, which will display to your console. -Pyramid does not make you use a single templating system exclusively. You -can use multiple templating systems, even in the same project. +:app:`Pyramid` has a debug toolbar that allows you to see information about how your application is working right in your browser. See configuration, installed packages, SQL queries, logging statements and more. -Example: :ref:`templates_used_directly`. +When your application has an error, an interactive debugger allows you to poke around from your browser to find out what happened. -Rendered views can return dictionaries -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -If you use a :term:`renderer`, you don't have to return a special kind of -"webby" ``Response`` object from a view. Instead, you can return a -dictionary, and Pyramid will take care of converting that dictionary -to a Response using a template on your behalf. This makes the view easier to -test, because you don't have to parse HTML in your tests; just make an -assertion instead that the view returns "the right stuff" in the dictionary -it returns. You can write "real" unit tests instead of functionally testing -all of your views. - -.. index:: - pair: renderer; explicitly calling - pair: view renderer; explictly calling +To use the :app:`Pyramid` debug toolbar, build your project with our :term:`cookiecutter`. -.. _example_render_to_response_call: - -For example, instead of returning a ``Response`` object from a -``render_to_response`` call: - -.. code-block:: python - :linenos: - - from pyramid.renderers import render_to_response - - def myview(request): - return render_to_response('myapp:templates/mytemplate.pt', {'a':1}, - request=request) - -You can return a Python dictionary: - -.. code-block:: python - :linenos: - - from pyramid.view import view_config - - @view_config(renderer='myapp:templates/mytemplate.pt') - def myview(request): - return {'a':1} - -When this view callable is called by Pyramid, the ``{'a':1}`` dictionary will -be rendered to a response on your behalf. The string passed as ``renderer=`` -above is an :term:`asset specification`. It is in the form -``packagename:directoryname/filename.ext``. In this case, it refers to the -``mytemplate.pt`` file in the ``templates`` directory within the ``myapp`` -Python package. Asset specifications are omnipresent in Pyramid: see -:ref:`intro_asset_specs` for more information. - -Example: :ref:`renderers_chapter`. - -Event system -~~~~~~~~~~~~ - -Pyramid emits *events* during its request processing lifecycle. You can -subscribe any number of listeners to these events. For example, to be -notified of a new request, you can subscribe to the ``NewRequest`` event. To -be notified that a template is about to be rendered, you can subscribe to the -``BeforeRender`` event, and so forth. Using an event publishing system as a -framework notification feature instead of hardcoded hook points tends to make -systems based on that framework less brittle. - -You can also use Pyramid's event system to send your *own* events. For -example, if you'd like to create a system that is itself a framework, and may -want to notify subscribers that a document has just been indexed, you can -create your own event type (``DocumentIndexed`` perhaps) and send the event -via Pyramid. Users of this framework can then subscribe to your event like -they'd subscribe to the events that are normally sent by Pyramid itself. - -Example: :ref:`events_chapter` and :ref:`event_types`. - -Built-in internationalization -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +.. seealso:: -Pyramid ships with internationalization-related features in its core: -localization, pluralization, and creating message catalogs from source files -and templates. Pyramid allows for a plurality of message catalog via the use -of translation domains: you can create a system that has its own translations -without conflict with other translations in other domains. + See also :ref:`debug_toolbar`. -Example: :ref:`i18n_chapter`. +Debug with power +~~~~~~~~~~~~~~~~ -HTTP caching -~~~~~~~~~~~~ +When things go wrong, :app:`Pyramid` gives you powerful ways to fix the problem. -Pyramid provides an easy way to associate views with HTTP caching policies. -You can just tell Pyramid to configure your view with an ``http_cache`` -statement, and it will take care of the rest:: +You can configure :app:`Pyramid` to print helpful information to the console. The ``debug_notfound`` setting shows information about URLs that aren't matched. The ``debug_authorization`` setting provides helpful messages about why you aren't allowed to do what you just tried. - @view_config(http_cache=3600) # 60 minutes - def myview(request): .... +:app:`Pyramid` also has command line tools to help you verify your configuration. You can use ``proutes`` and ``pviews`` to inspect how URLs are connected to your application code. -Pyramid will add appropriate ``Cache-Control`` and ``Expires`` headers to -responses generated when this view is invoked. +.. seealso:: -See the :meth:`~pyramid.config.Configurator.add_view` method's -``http_cache`` documentation for more information. + See also :ref:`debug_authorization_section`, :ref:`command_line_chapter`, + and :doc:`../pscripts/index` -Sessions -~~~~~~~~ +Extend your application +~~~~~~~~~~~~~~~~~~~~~~~ -Pyramid has built-in HTTP sessioning. This allows you to associate data with -otherwise anonymous users between requests. Lots of systems do this. But -Pyramid also allows you to plug in your own sessioning system by creating some -code that adheres to a documented interface. Currently there is a binding -package for the third-party Redis sessioning system that does exactly this. -But if you have a specialized need (perhaps you want to store your session data -in MongoDB), you can. You can even switch between implementations without -changing your application code. +:app:`Pyramid` add-ons extend the core of the framework with useful abilities. There are add-ons available for your favorite template language, SQL and NoSQL databases, authentication services and more. -Example: :ref:`sessions_chapter`. +Supported :app:`Pyramid` add-ons are held to the same demanding standards as the framework itself. You will find them to be fully tested and well documented. -Speed -~~~~~ - -The Pyramid core is, as far as we can tell, at least marginally faster than -any other existing Python web framework. It has been engineered from the -ground up for speed. It only does as much work as absolutely necessary when -you ask it to get a job done. Extraneous function calls and suboptimal -algorithms in its core codepaths are avoided. It is feasible to get, for -example, between 3500 and 4000 requests per second from a simple Pyramid view -on commodity dual-core laptop hardware and an appropriate WSGI server -(mod_wsgi or gunicorn). In any case, performance statistics are largely -useless without requirements and goals, but if you need speed, Pyramid will -almost certainly never be your application's bottleneck; at least no more -than Python will be a bottleneck. - -Example: http://blog.curiasolutions.com/the-great-web-framework-shootout/ - -Exception views -~~~~~~~~~~~~~~~ - -Exceptions happen. Rather than deal with exceptions that might present -themselves to a user in production in an ad-hoc way, Pyramid allows you to -register an :term:`exception view`. Exception views are like regular Pyramid -views, but they're only invoked when an exception "bubbles up" to Pyramid -itself. For example, you might register an exception view for the -:exc:`Exception` exception, which will catch *all* exceptions, and present a -pretty "well, this is embarrassing" page. Or you might choose to register an -exception view for only specific kinds of application-specific exceptions, -such as an exception that happens when a file is not found, or an exception -that happens when an action cannot be performed because the user doesn't have -permission to do something. In the former case, you can show a pretty "Not -Found" page; in the latter case you might show a login form. +.. seealso:: -Example: :ref:`exception_views`. + See also https://trypyramid.com/extending-pyramid.html -No singletons -~~~~~~~~~~~~~ - -Pyramid is written in such a way that it requires your application to have -exactly zero "singleton" data structures. Or, put another way, Pyramid -doesn't require you to construct any "mutable globals". Or put even a -different way, an import of a Pyramid application needn't have any -"import-time side effects". This is esoteric-sounding, but if you've ever -tried to cope with parameterizing a Django "settings.py" file for multiple -installations of the same application, or if you've ever needed to -monkey-patch some framework fixture so that it behaves properly for your use -case, or if you've ever wanted to deploy your system using an asynchronous -server, you'll end up appreciating this feature. It just won't be a problem. -You can even run multiple copies of a similar but not identically configured -Pyramid application within the same Python process. This is good for shared -hosting environments, where RAM is at a premium. - -View predicates and many views per route -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Unlike many other systems, Pyramid allows you to associate more than one view -per route. For example, you can create a route with the pattern ``/items`` -and when the route is matched, you can shuffle off the request to one view if -the request method is GET, another view if the request method is POST, etc. -A system known as "view predicates" allows for this. Request method matching -is the most basic thing you can do with a view predicate. You can also -associate views with other request parameters such as the elements in the -query string, the Accept header, whether the request is an XHR request or -not, and lots of other things. This feature allows you to keep your -individual views "clean"; they won't need much conditional logic, so they'll -be easier to test. - -Example: :ref:`view_configuration_parameters`. - -Transaction management -~~~~~~~~~~~~~~~~~~~~~~ +Write your views, *your* way +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Pyramid's :term:`scaffold` system renders projects that include a -*transaction management* system, stolen from Zope. When you use this -transaction management system, you cease being responsible for committing -your data anymore. Instead, Pyramid takes care of committing: it commits at -the end of a request or aborts if there's an exception. Why is that a good -thing? Having a centralized place for transaction management is a great -thing. If, instead of managing your transactions in a centralized place, you -sprinkle ``session.commit`` calls in your application logic itself, you can -wind up in a bad place. Wherever you manually commit data to your database, -it's likely that some of your other code is going to run *after* your commit. -If that code goes on to do other important things after that commit, and an -error happens in the later code, you can easily wind up with inconsistent -data if you're not extremely careful. Some data will have been written to -the database that probably should not have. Having a centralized commit -point saves you from needing to think about this; it's great for lazy people -who also care about data integrity. Either the request completes -successfully, and all changes are committed, or it does not, and all changes -are aborted. - -Also, Pyramid's transaction management system allows you to synchronize -commits between multiple databases, and allows you to do things like -conditionally send email if a transaction commits, but otherwise keep quiet. - -Example: :ref:`bfg_sql_wiki_tutorial` (note the lack of commit statements -anywhere in application code). - -Configuration conflict detection -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +A fundamental task for any framework is to map URLs to code. In :app:`Pyramid`, that code is called a :term:`view callable`. View callables can be functions, class methods or even callable class instances. You are free to choose the approach that best fits your use case. Regardless of your choice, :app:`Pyramid` treats them the same. You can change your mind at any time without any penalty. There are no artificial distinctions between the various approaches. -When a system is small, it's reasonably easy to keep it all in your head. -But when systems grow large, you may have hundreds or thousands of -configuration statements which add a view, add a route, and so forth. -Pyramid's configuration system keeps track of your configuration statements, -and if you accidentally add two that are identical, or Pyramid can't make -sense out of what it would mean to have both statements active at the same -time, it will complain loudly at startup time. It's not dumb though: it will -automatically resolve conflicting configuration statements on its own if you -use the configuration :meth:`~pyramid.config.Configurator.include` system: -"more local" statements are preferred over "less local" ones. This allows -you to intelligently factor large systems into smaller ones. - -Example: :ref:`conflict_detection`. - -Configuration extensibility -~~~~~~~~~~~~~~~~~~~~~~~~~~~ - -Unlike other systems, Pyramid provides a structured "include" mechanism (see -:meth:`~pyramid.config.Configurator.include`) that allows you to combine -applications from multiple Python packages. All the configuration statements -that can be performed in your "main" Pyramid application can also be -performed by included packages including the addition of views, routes, -subscribers, and even authentication and authorization policies. You can even -extend or override an existing application by including another application's -configuration in your own, overriding or adding new views and routes to -it. This has the potential to allow you to create a big application out of -many other smaller ones. For example, if you want to reuse an existing -application that already has a bunch of routes, you can just use the -``include`` statement with a ``route_prefix``; the new application will live -within your application at a URL prefix. It's not a big deal, and requires -little up-front engineering effort. - -For example: +Here's a view callable defined as a function: .. code-block:: python - :linenos: + :linenos: - from pyramid.config import Configurator + from pyramid.response import Response + from pyramid.view import view_config - if __name__ == '__main__': - config = Configurator() - config.include('pyramid_jinja2') - config.include('pyramid_exclog') - config.include('some.other.guys.package', route_prefix='/someotherguy') + @view_config(route_name='aview') + def aview(request): + return Response('one') -.. seealso:: +Here's a few views defined as methods of a class instead: - See also :ref:`including_configuration` and - :ref:`building_an_extensible_app`. +.. code-block:: python + :linenos: -Flexible authentication and authorization -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + from pyramid.response import Response + from pyramid.view import view_config -Pyramid includes a flexible, pluggable authentication and authorization -system. No matter where your user data is stored, or what scheme you'd like -to use to permit your users to access your data, you can use a predefined -Pyramid plugpoint to plug in your custom authentication and authorization -code. If you want to change these schemes later, you can just change it in -one place rather than everywhere in your code. It also ships with prebuilt -well-tested authentication and authorization schemes out of the box. But -what if you don't want to use Pyramid's built-in system? You don't have to. -You can just write your own bespoke security code as you would in any other -system. + class AView(object): + def __init__(self, request): + self.request = request -Example: :ref:`enabling_authorization_policy`. + @view_config(route_name='view_one') + def view_one(self): + return Response('one') -Traversal -~~~~~~~~~ + @view_config(route_name='view_two') + def view_two(self): + return Response('two') -:term:`Traversal` is a concept stolen from :term:`Zope`. It allows you to -create a tree of resources, each of which can be addressed by one or more -URLs. Each of those resources can have one or more *views* associated with -it. If your data isn't naturally treelike (or you're unwilling to create a -treelike representation of your data), you aren't going to find traversal -very useful. However, traversal is absolutely fantastic for sites that need -to be arbitrarily extensible: it's a lot easier to add a node to a tree than -it is to shoehorn a route into an ordered list of other routes, or to create -another entire instance of an application to service a department and glue -code to allow disparate apps to share data. It's a great fit for sites that -naturally lend themselves to changing departmental hierarchies, such as -content management systems and document management systems. Traversal also -lends itself well to systems that require very granular security ("Bob can -edit *this* document" as opposed to "Bob can edit documents"). - -Examples: :ref:`hello_traversal_chapter` and -:ref:`much_ado_about_traversal_chapter`. - -Tweens -~~~~~~ +.. seealso:: -Pyramid has a sort of internal WSGI-middleware-ish pipeline that can be hooked -by arbitrary add-ons named "tweens". The debug toolbar is a "tween", and the -``pyramid_tm`` transaction manager is also. Tweens are more useful than WSGI -:term:`middleware` in some circumstances because they run in the context of -Pyramid itself, meaning you have access to templates and other renderers, a -"real" request object, and other niceties. + See also :ref:`view_config_placement`. -Example: :ref:`registering_tweens`. +.. _intro_asset_specs: -View response adapters -~~~~~~~~~~~~~~~~~~~~~~ +Find *your* static assets +~~~~~~~~~~~~~~~~~~~~~~~~~ -A lot is made of the aesthetics of what *kinds* of objects you're allowed to -return from view callables in various frameworks. In a previous section in -this document we showed you that, if you use a :term:`renderer`, you can -usually return a dictionary from a view callable instead of a full-on -:term:`Response` object. But some frameworks allow you to return strings or -tuples from view callables. When frameworks allow for this, code looks -slightly prettier, because fewer imports need to be done, and there is less -code. For example, compare this: +In many web frameworks, the static assets required by an application are kept in a globally shared location, "the *static* directory". Others use a lookup scheme, like an ordered set of template directories. Both of these approaches have problems when it comes to customization. -.. code-block:: python - :linenos: +:app:`Pyramid` takes a different approach. Static assets are located using *asset specifications*, strings that contain reference both to a Python package name and a file or directory name, e.g. ``MyPackage:static/index.html``. These specifications are used for templates, JavaScript and CSS, translation files, and any other package-bound static resource. By using asset specifications, :app:`Pyramid` makes it easy to extend your application with other packages without worrying about conflicts. - def aview(request): - return "Hello world!" +What happens if another :app:`Pyramid` package you are using provides an asset you need to customize? Maybe that page template needs better HTML, or you want to update some CSS. With asset specifications you can override the assets from other packages using simple wrappers. -To this: - -.. code-block:: python - :linenos: +Examples: :ref:`asset_specifications` and :ref:`overriding_assets_section`. - from pyramid.response import Response +Use *your* templates +~~~~~~~~~~~~~~~~~~~~ - def aview(request): - return Response("Hello world!") +In :app:`Pyramid`, the job of creating a ``Response`` belongs to a :term:`renderer`. Any templating system—Mako, Chameleon, Jinja2—can be a renderer. In fact, packages exist for all of these systems. But if you'd rather use another, a structured API exists allowing you to create a renderer using your favorite templating system. You can use the templating system *you* understand, not one required by the framework. -The former is "prettier", right? +What's more, :app:`Pyramid` does not make you use a single templating system exclusively. You can use multiple templating systems, even in the same project. -Out of the box, if you define the former view callable (the one that simply -returns a string) in Pyramid, when it is executed, Pyramid will raise an -exception. This is because "explicit is better than implicit", in most -cases, and by default, Pyramid wants you to return a :term:`Response` object -from a view callable. This is because there's usually a heck of a lot more -to a response object than just its body. But if you're the kind of person -who values such aesthetics, we have an easy way to allow for this sort of -thing: +Example: :ref:`templates_used_directly`. -.. code-block:: python - :linenos: +Write testable views +~~~~~~~~~~~~~~~~~~~~ - from pyramid.config import Configurator - from pyramid.response import Response +When you use a :term:`renderer` with your view callable, you are freed from needing to return a "webby" ``Response`` object. Instead your views can return a simple Python dictionary. :app:`Pyramid` will take care of rendering the information in that dictionary to a ``Response`` on your behalf. As a result, your views are more easily tested, since you don't need to parse HTML to evaluate the results. :app:`Pyramid` makes it a snap to write unit tests for your views, instead of requiring you to use functional tests. - def string_response_adapter(s): - response = Response(s) - response.content_type = 'text/html' - return response +.. index:: + pair: renderer; explicitly calling + pair: view renderer; explictly calling - if __name__ == '__main__': - config = Configurator() - config.add_response_adapter(string_response_adapter, basestring) +.. _example_render_to_response_call: -Do that once in your Pyramid application at startup. Now you can return -strings from any of your view callables, e.g.: +For example, a typical web framework might return a ``Response`` object from a ``render_to_response`` call: .. code-block:: python - :linenos: + :linenos: - def helloview(request): - return "Hello world!" + from pyramid.renderers import render_to_response - def goodbyeview(request): - return "Goodbye world!" + def myview(request): + return render_to_response('myapp:templates/mytemplate.pt', {'a':1}, + request=request) -Oh noes! What if you want to indicate a custom content type? And a custom -status code? No fear: +While you *can* do this in :app:`Pyramid`, you can also return a Python dictionary: .. code-block:: python - :linenos: - - from pyramid.config import Configurator - - def tuple_response_adapter(val): - status_int, content_type, body = val - response = Response(body) - response.content_type = content_type - response.status_int = status_int - return response - - def string_response_adapter(body): - response = Response(body) - response.content_type = 'text/html' - response.status_int = 200 - return response - - if __name__ == '__main__': - config = Configurator() - config.add_response_adapter(string_response_adapter, basestring) - config.add_response_adapter(tuple_response_adapter, tuple) - -Once this is done, both of these view callables will work: + :linenos: -.. code-block:: python - :linenos: + from pyramid.view import view_config - def aview(request): - return "Hello world!" + @view_config(renderer='myapp:templates/mytemplate.pt') + def myview(request): + return {'a':1} - def anotherview(request): - return (403, 'text/plain', "Forbidden") +By configuring your view to use a renderer, you tell :app:`Pyramid` to use the ``{'a':1}`` dictionary and the specified template to render a response on your behalf. -Pyramid defaults to explicit behavior, because it's the most generally -useful, but provides hooks that allow you to adapt the framework to localized -aesthetic desires. +The string passed as ``renderer=`` above is an :term:`asset specification`. Asset specifications are widely used in :app:`Pyramid`. They allow for more reliable customization. See :ref:`intro_asset_specs` for more information. -.. seealso:: +Example: :ref:`renderers_chapter`. - See also :ref:`using_iresponse`. +Use events to coordinate actions +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -"Global" response object -~~~~~~~~~~~~~~~~~~~~~~~~ +When writing web applications, it is often important to have your code run at a specific point in the lifecycle of a request. In :app:`Pyramid`, you can accomplish this using *subscribers* and *events*. -"Constructing these response objects in my view callables is such a chore! -And I'm way too lazy to register a response adapter, as per the prior -section," you say. Fine. Be that way: +For example, you might have a job that needs to be done each time your application handles a new request. :app:`Pyramid` emits a ``NewRequest`` event at this point in the request handling lifecycle. You can register your code as a subscriber to this event using a clear, declarative style: .. code-block:: python - :linenos: - def aview(request): - response = request.response - response.body = 'Hello world!' - response.content_type = 'text/plain' - return response + from pyramid.events import NewRequest + from pyramid.events import subscriber -.. seealso:: + @subscriber(NewRequest) + def my_job(event): + do_something(event.request) - See also :ref:`request_response_attr`. +:app:`Pyramid`\ 's event system can be extended as well. If you need, you can create events of your own and send them using :app:`Pyramid`\ 's event system. Then anyone working with your application can subscribe to your events and coordinate their code with yours. -Automating repetitive configuration -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Example: :ref:`events_chapter` and :ref:`event_types`. -Does Pyramid's configurator allow you to do something, but you're a little -adventurous and just want it a little less verbose? Or you'd like to offer -up some handy configuration feature to other Pyramid users without requiring -that we change Pyramid? You can extend Pyramid's :term:`Configurator` with -your own directives. For example, let's say you find yourself calling -:meth:`pyramid.config.Configurator.add_view` repetitively. Usually you can -take the boring away by using existing shortcuts, but let's say that this is -a case where there is no such shortcut: +Build international applications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -.. code-block:: python - :linenos: +:app:`Pyramid` ships with internationalization-related features in its core: localization, pluralization, and creating message catalogs from source files and templates. :app:`Pyramid` allows for a plurality of message catalogs via the use of translation domains. You can create a system that has its own translations without conflict with other translations in other domains. - from pyramid.config import Configurator +Example: :ref:`i18n_chapter`. - config = Configurator() - config.add_route('xhr_route', '/xhr/{id}') - config.add_view('my.package.GET_view', route_name='xhr_route', - xhr=True, permission='view', request_method='GET') - config.add_view('my.package.POST_view', route_name='xhr_route', - xhr=True, permission='view', request_method='POST') - config.add_view('my.package.HEAD_view', route_name='xhr_route', - xhr=True, permission='view', request_method='HEAD') +Build efficient applications +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Pretty tedious right? You can add a directive to the Pyramid configurator to -automate some of the tedium away: +:app:`Pyramid` provides an easy way to *cache* the results of slow or expensive views. You can indicate in view configuration that you want a view to be cached: .. code-block:: python - :linenos: - from pyramid.config import Configurator + @view_config(http_cache=3600) # 60 minutes + def myview(request): + # ... - def add_protected_xhr_views(config, module): - module = config.maybe_dotted(module) - for method in ('GET', 'POST', 'HEAD'): - view = getattr(module, 'xhr_%s_view' % method, None) - if view is not None: - config.add_view(view, route_name='xhr_route', xhr=True, - permission='view', request_method=method) +:app:`Pyramid` will automatically add the appropriate ``Cache-Control`` and ``Expires`` headers to the response it creates. - config = Configurator() - config.add_directive('add_protected_xhr_views', add_protected_xhr_views) +See the :meth:`~pyramid.config.Configurator.add_view` method's ``http_cache`` documentation for more information. -Once that's done, you can call the directive you've just added as a method of -the Configurator object: +Build fast applications +~~~~~~~~~~~~~~~~~~~~~~~ -.. code-block:: python - :linenos: +The :app:`Pyramid` core is fast. It has been engineered from the ground up for speed. It only does as much work as absolutely necessary when you ask it to get a job done. If you need speed from your application, :app:`Pyramid` is the right choice for you. - config.add_route('xhr_route', '/xhr/{id}') - config.add_protected_xhr_views('my.package') +Example: https://blog.curiasolutions.com/pages/the-great-web-framework-shootout.html -Your previously repetitive configuration lines have now morphed into one line. +Store session data +~~~~~~~~~~~~~~~~~~ -You can share your configuration code with others this way too by packaging -it up and calling :meth:`~pyramid.config.Configurator.add_directive` from -within a function called when another user uses the -:meth:`~pyramid.config.Configurator.include` method against your code. +:app:`Pyramid` has built-in support for HTTP sessions, so you can associate data with specific users between requests. Lots of other frameworks also support sessions. But :app:`Pyramid` allows you to plug in your own custom sessioning system. So long as your system conforms to a documented interface, you can drop it in in place of the provided system. -.. seealso:: +Currently there is a binding package for the third-party Redis sessioning system that does exactly this. But if you have a specialized need (perhaps you want to store your session data in MongoDB), you can. You can even switch between implementations without changing your application code. - See also :ref:`add_directive`. +Example: :ref:`sessions_chapter`. -Programmatic Introspection +Handle problems with grace ~~~~~~~~~~~~~~~~~~~~~~~~~~ -If you're building a large system that other users may plug code into, it's -useful to be able to get an enumeration of what code they plugged in *at -application runtime*. For example, you might want to show them a set of tabs -at the top of the screen based on an enumeration of views they registered. - -This is possible using Pyramid's :term:`introspector`. +Mistakes happen. Problems crop up. No one writes bug-free code. :app:`Pyramid`provides a way to handle the exceptions your code encounters. An :term:`exception view` is a special kind of view which is automatically called when a particular exception type arises without being handled by your application. -Here's an example of using Pyramid's introspector from within a view -callable: +For example, you might register an exception view for the :exc:`Exception` exception type, which will catch *all* exceptions, and present a pretty "well, this is embarrassing" page. Or you might choose to register an exception view for only certain application-specific exceptions. You can make one for when a file is not found, or when the user doesn't have permission to do something. In the former case, you can show a pretty "Not Found" page; in the latter case you might show a login form. -.. code-block:: python - :linenos: - - from pyramid.view import view_config - from pyramid.response import Response - - @view_config(route_name='bar') - def show_current_route_pattern(request): - introspector = request.registry.introspector - route_name = request.matched_route.name - route_intr = introspector.get('routes', route_name) - return Response(str(route_intr['pattern'])) - -.. seealso:: - - See also :ref:`using_introspection`. +Example: :ref:`exception_views`. -Python 3 Compatibility +And much, much more... ~~~~~~~~~~~~~~~~~~~~~~ -Pyramid and most of its add-ons are Python 3 compatible. If you develop a -Pyramid application today, you won't need to worry that five years from now -you'll be backwatered because there are language features you'd like to use -but your framework doesn't support newer Python versions. +:app:`Pyramid` has been built with a number of other sophisticated design features that make it adaptable. Read more about them below. -Testing -~~~~~~~ +.. toctree:: + :maxdepth: 2 -Every release of Pyramid has 100% statement coverage via unit and integration -tests, as measured by the ``coverage`` tool available on PyPI. It also has -greater than 95% decision/condition coverage as measured by the -``instrumental`` tool available on PyPI. It is automatically tested by the -Jenkins tool on Python 2.6, Python 2.7, Python 3.2 and PyPy after each commit -to its GitHub repository. Official Pyramid add-ons are held to a similar -testing standard. We still find bugs in Pyramid and its official add-ons, -but we've noticed we find a lot more of them while working on other projects -that don't have a good testing regime. + advanced-features -Example: http://jenkins.pylonsproject.org/ -Support -~~~~~~~ -It's our goal that no Pyramid question go unanswered. Whether you ask a -question on IRC, on the Pylons-discuss maillist, or on StackOverflow, you're -likely to get a reasonably prompt response. We don't tolerate "support -trolls" or other people who seem to get their rocks off by berating fellow -users in our various official support channels. We try to keep it well-lit -and new-user-friendly. -Example: Visit irc\://freenode.net#pyramid (the ``#pyramid`` channel on -irc.freenode.net in an IRC client) or the pylons-discuss maillist at -http://groups.google.com/group/pylons-discuss/ . - -Documentation -~~~~~~~~~~~~~ - -It's a constant struggle, but we try to maintain a balance between -completeness and new-user-friendliness in the official narrative Pyramid -documentation (concrete suggestions for improvement are always appreciated, -by the way). We also maintain a "cookbook" of recipes, which are usually -demonstrations of common integration scenarios, too specific to add to the -official narrative docs. In any case, the Pyramid documentation is -comprehensive. - -Example: The rest of this documentation and the cookbook at -http://docs.pylonsproject.org/projects/pyramid_cookbook/dev/ . .. index:: single: Pylons Project @@ -913,10 +364,7 @@ http://docs.pylonsproject.org/projects/pyramid_cookbook/dev/ . What Is The Pylons Project? --------------------------- -:app:`Pyramid` is a member of the collection of software published under the -Pylons Project. Pylons software is written by a loose-knit community of -contributors. The `Pylons Project website <http://pylonsproject.org>`_ -includes details about how :app:`Pyramid` relates to the Pylons Project. +:app:`Pyramid` is a member of the collection of software published under the Pylons Project. Pylons software is written by a loose-knit community of contributors. The `Pylons Project website <https://pylonsproject.org>`_ includes details about how :app:`Pyramid` relates to the Pylons Project. .. index:: single: pyramid and other frameworks @@ -926,72 +374,16 @@ includes details about how :app:`Pyramid` relates to the Pylons Project. single: MVC :app:`Pyramid` and Other Web Frameworks ------------------------------------------- - -The first release of Pyramid's predecessor (named :mod:`repoze.bfg`) was made -in July of 2008. At the end of 2010, we changed the name of -:mod:`repoze.bfg` to :app:`Pyramid`. It was merged into the Pylons project -as :app:`Pyramid` in November of that year. - -:app:`Pyramid` was inspired by :term:`Zope`, :term:`Pylons` (version -1.0) and :term:`Django`. As a result, :app:`Pyramid` borrows several -concepts and features from each, combining them into a unique web -framework. - -Many features of :app:`Pyramid` trace their origins back to :term:`Zope`. -Like Zope applications, :app:`Pyramid` applications can be easily extended: -if you obey certain constraints, the application you produce can be reused, -modified, re-integrated, or extended by third-party developers without -forking the original application. The concepts of :term:`traversal` and -declarative security in :app:`Pyramid` were pioneered first in Zope. - -The :app:`Pyramid` concept of :term:`URL dispatch` is inspired by the -:term:`Routes` system used by :term:`Pylons` version 1.0. Like Pylons -version 1.0, :app:`Pyramid` is mostly policy-free. It makes no -assertions about which database you should use, and its built-in -templating facilities are included only for convenience. In essence, -it only supplies a mechanism to map URLs to :term:`view` code, along -with a set of conventions for calling those views. You are free to -use third-party components that fit your needs in your applications. - -The concept of :term:`view` is used by :app:`Pyramid` mostly as it would be -by Django. :app:`Pyramid` has a documentation culture more like Django's -than like Zope's. - -Like :term:`Pylons` version 1.0, but unlike :term:`Zope`, a :app:`Pyramid` -application developer may use completely imperative code to perform common -framework configuration tasks such as adding a view or a route. In Zope, -:term:`ZCML` is typically required for similar purposes. In :term:`Grok`, a -Zope-based web framework, :term:`decorator` objects and class-level -declarations are used for this purpose. Out of the box, Pyramid supports -imperative and decorator-based configuration; :term:`ZCML` may be used via an -add-on package named ``pyramid_zcml``. - -Also unlike :term:`Zope` and unlike other "full-stack" frameworks such -as :term:`Django`, :app:`Pyramid` makes no assumptions about which -persistence mechanisms you should use to build an application. Zope -applications are typically reliant on :term:`ZODB`; :app:`Pyramid` -allows you to build :term:`ZODB` applications, but it has no reliance -on the ZODB software. Likewise, :term:`Django` tends to assume that -you want to store your application's data in a relational database. -:app:`Pyramid` makes no such assumption; it allows you to use a -relational database but doesn't encourage or discourage the decision. - -Other Python web frameworks advertise themselves as members of a class -of web frameworks named `model-view-controller -<http://en.wikipedia.org/wiki/Model–view–controller>`_ frameworks. -Insofar as this term has been claimed to represent a class of web -frameworks, :app:`Pyramid` also generally fits into this class. - -.. sidebar:: You Say :app:`Pyramid` is MVC, But Where's The Controller? - - The :app:`Pyramid` authors believe that the MVC pattern just doesn't - really fit the web very well. In a :app:`Pyramid` application, there is a - resource tree, which represents the site structure, and views, which tend - to present the data stored in the resource tree and a user-defined "domain - model". However, no facility provided *by the framework* actually - necessarily maps to the concept of a "controller" or "model". So if you - had to give it some acronym, I guess you'd say :app:`Pyramid` is actually - an "RV" framework rather than an "MVC" framework. "MVC", however, is - close enough as a general classification moniker for purposes of - comparison with other web frameworks. +--------------------------------------- + +The first release of :app:`Pyramid`\ 's predecessor (named :mod:`repoze.bfg`) was made in July of 2008. At the end of 2010, we changed the name of :mod:`repoze.bfg` to :app:`Pyramid`. It was merged into the Pylons project as :app:`Pyramid` in November of that year. + +:app:`Pyramid` was inspired by :term:`Zope`, :term:`Pylons` (version 1.0), and :term:`Django`. As a result, :app:`Pyramid` borrows several concepts and features from each, combining them into a unique web framework. + +Similar to :term:`Zope`, :app:`Pyramid` applications may easily be extended. If you work within the constraints of the framework, you can produce applications that can be reused, modified, or extended without needing to modify the original application code. :app:`Pyramid` also inherits the concepts of :term:`traversal` and declarative security from Zope. + +Similar to :term:`Pylons` version 1.0, :app:`Pyramid` is largely free of policy. It makes no assertions about which database or template system you should use. You are free to use whatever third-party components fit the needs of your specific application. :app:`Pyramid` also inherits its approach to :term:`URL dispatch` from Pylons. + +Similar to :term:`Django`, :app:`Pyramid` values extensive documentation. In addition, the concept of a :term:`view` is used by :app:`Pyramid` much as it would be by Django. + +Other Python web frameworks advertise themselves as members of a class of web frameworks named `model-view-controller <https://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller>`_ frameworks. The authors of :app:`Pyramid` do not believe that the MVC pattern fits the web particularly well. However, if this abstraction works for you, :app:`Pyramid` also generally fits into this class. |