Home > Articles > Open Source > Python

An Introduction to Python Web Development Using the Pyramid Framework Part 2

In Part 2 of his seven-part series on learning Python Pyramid, Jesse Smith looks at how to configure a Pyramid application by using Imperative and Declarative configurations.
Like this article? We recommend

If you haven't read Part 1 of this series, I recommend you do that before continuing with this article. In Part 1, we looked at the installation of the Python framework, along with creating your first scaffolding app.

This article dives deeper into how the Pyramid framework works from a configuration standpoint. I'll outline the process of initializing an application by connecting a web server to an application server instance, along with how to add application views. The web server on which the framework runs is called Waitress. It's a production-quality server for hosting web applications.

To get started, we'll first examine types of application configuration used by Pyramid. The Pyramid documentation covers some of this information; however, the purpose of this article is not only to clarify these concepts further, but to address some missing analysis. Often, the documentation leaves gaps in coverage and isn't concise or understandable. If you continue reading and using these articles as a reference, you'll be on the fast track to developing web applications using Python Pyramid.

Application Configuration

Python has two types of application configuration: Imperative Configuration (IC) and Declarative Configuration (DC). As with most other languages, you can either configure the app settings programmatically or by using the configuration files. IC and DC are both done programmatically as part of the application's code base. I'm not a big fan of this approach because it doesn't loosely couple the configuration settings from the application code. However, this approach is just as commonly used to create static settings in a configuration file. IC refers to the process of configuring an app by using simple Python statements with the Configurator object, as in the following example:

from wsgiref.simple_server import make_server

from pyramid.config import Configurator
from pyramid.response import Response

def hello_world(request):
    return Response('Hello world!')

if __name__ == '__main__':
    config = Configurator()
    config.add_view(hello_world)
    app = config.make_wsgi_app()
    server = make_server('0.0.0.0', 8080, app)
    server.serve_forever()

The important thing to note here is the Configurator object, which is used to configure the application registry. This registry is a repository of configuration information for the application. An application can only have one registry. The add_view method of the Configurator object maps a request object to a callable response object, using the hello_world method. These objects are similar to the HTTP Request and Response objects in Java or .NET.

The make_wsgi_app() method returns a Web Server Gateway Interface (WSGI) application instance for the application. The instance is returned as a result of connecting the web server to the application. However, the hosting process isn't complete without the make_server object. This object creates an instance of an application server on which the application can run. The app object is passed in to connect the application server to the web server, much like Java Servlets do for Java. The port that the web server will use, 8080, is also passed to this method. The serve_forever() method will keep serving requests until Ctrl-C is used to stop the server.

The second type of configuration, Declarative Configuration, uses metadata invocations for setting up view directives, as in the following example:

from pyramid.response import Response
from pyramid.view import view_config

@view_config(name='hello', request_method='GET')
def hello(request):
    return Response('Hello')

In this example, DC uses the view_config decorator, which allows us to add the @view_config attribute to represent our hello function. Attributes in this context are similar to .NET attributes and Java annotations. They essentially serve the same purpose, which is to mark up methods in your application that later inject code where the attribute is used. However, the Python version of using attributes is incomplete until the Configuration object's scan method is used. Here's a more complete example using scan:

from wsgiref.simple_server import make_server

from pyramid.config import Configurator
from pyramid.response import Response
from pyramid.view import view_config

@view_config()
def hello(request):
    return Response('Hello')

if __name__ == '__main__':
    from pyramid.config import Configurator
    config = Configurator()
    config.scan()
    app = config.make_wsgi_app()
    server = make_server('0.0.0.0', 8080, app)
    server.serve_forever()

Using a configuration decoration and scan together is referred to as a Declarative Configuration. The scan method scans for attributes and registers them to the application registry. DC ends up being shorthand for IC. In these examples, the DC version doesn't have to make a call to the add_view method, as the IC version does. Once scanned, it's called implicitly through the attribute. IC and DC achieve equivalent functionality with a view configuration. In simple terms, a view configuration is the process of mapping a request to a view. In the Model-View-Controller (MVC) world of application design, you can think of it as the View.

Conclusion

In this article, you learned the basics of configuration for Python Pyramid web applications using Declarative and Imperative view configuration approaches. The two approaches are essentially the same, but the DC approach uses attributes to substitute for view-configuration method calls. Neither approach is better than the other; use whichever you prefer. You should also be aware that using these programmatic methods of configuring your app replaces static configuration files such as development.ini and production.ini. In Part 3 of this series, I'll go over the detailed startup lifecycle of a Pyramid application and the anatomy of the .ini files.

At this stage, you should be quite comfortable setting up Pyramid web applications. But this article is only meant to serve as a simple starting point for configuring Pyramid applications. You should do some research and exploring on your own as well. When you do, you'll find that Python Pyramid is a powerful platform for web application development.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020