Writing a Django e-commerce framework

Django is well-suited for e-commerce, and there are currently several nascent django e-commerce frameworks in development. This talk is about the development of django-oscar, a framework designed to leverage Django's core functionality to allow domain-driven e-commerce applications to be built. This is a very powerful approach.

Writing django apps which are flexible enough to be adapted to a wide variety of
scenarios is a non-trivial problem which will be explored. The talk will also
cover a range of e-commerce best practices and how they can be implemented in
Django.

Transcript

1. Writing a Django e-commerce framework David Winterbottom @codeinthehole
2. Synopsis • Background / challenges • Why django / python • Customising django apps • E-commerce tips
6. Background
7. • 5 years of e-commerce projects • PHP / Python / Django • Lots of war stories
8. Books
9. Bookshop domain • Millions of products • ISBNs, BIC categories, authors, publishers • Automated feed-driven processing • Catalogue • Stock • Rich data
10. Two tier structure • Application tier - serves HTTP requests • Processing tier • Download and import feeds • Data cleaning and processing
11. More books
12. Different... • Fulfilment partners • Stock logic • Payment partners • Multiple payment sources • Complicated offers • eBooks!
13. PHP framework • Customisation via include path overrides • Lots of duplication • Hard to upgrade • Not-invented-here syndrome
14. Nailvarnish
15. T-shirts
16. Digital music
17. Bar equipment
18. New requirements • Product variations - colours, sizes etc • New fulfilment processes • Pricing models
19. B2B • Sales reps • Tax rules • Managed budgets • Integration with “enterprise” software
20. • Original assumptions all broken • Domains vary wildly • Lots of work-arounds
22. Requirements • Agnostic - few assumptions as possible • Models domain • without duplication • without too much meta-data
23. EAV ENTITY ATTRIBUTE VALUE Product Weight 150 Order Cost centre ZPAN
26. • Leather gloves
27. Bendy bits
28. Taxonomy
29. Stock
30. Shipping
31. Payment
32. and also...
34. Nothing is sacred
37. django-oscar • Django 1.3 • Experience of last 5 years baked into models • Lean core • Different customisation path
39. Lots of others • Satchmo • Lightning-Fast-Shop • Satchless • Django-shop • Plata, Mamona, Cartridge, ... • http://djangopackages.com/grids/g/ecommerce/
41. Decimals
45. kwargs
46. Shipping calculator
47. PHP
55. Python
58. Web framework • Well-thought out structure • Templating, HTTP, caching, ... • Good test support • Security • Class-based views
59. Models • Models drive the design • Capture domain logic • Foundation for rest of application
60. Eco-system • Haystack (search) • South (database migrations) • Celery (job queue) • Internal libraries
62. Customisation
63. Techniques
64. DEBUG = True settings.py
65. AUTH_PROFILE_MODULE = ‘customer.Profile’ settings.py
66. Key idea • Having the same name/identifier as your parent • Subclass and override
67. Templates
72. Django looks here first
73. Views
74. Oscar default
75. urls.py
76. oscar/app.py
77. oscar/core/app.py
78. oscar/apps/checkout/app.py
79. Oscar project
80. Replace application urls.py
81. myproject/app.py Use different app instance
82. myproject/checkout/app.py Use different view classes
83. myproject/checkout/views.py Override and extend method
84. Models
85. Oscar default
86. settings.py
87. abstract_models.py
88. models.py
89. Oscar project
90. replaces oscar app settings.py same ‘app label’
91. add custom fields myproject/voucher/models.py import remaining models
92. templatetags management commands fixtures settings.py
93. Classes
94. model name ‘app label’
95. module path class name
96. use same class name as in core
97. Recap • Bit of a work-around... • ...but works well • Applicable to other django libraries
98. Best practices
99. Log everything ...except bankcard details.
100. Audit models
102. Monitor everything watch high and low thresholds
103. SOA • Services make your life easier • Keep a layer in front of your models • Facade design pattern
104. View
105. View Models Database Load business objects
106. View Service Models Database Load business objects Business logic here
107. View Service Models Database Load business objects Business logic here
108. View Service Models Database Load business objects Business logic here
109. Rules of thumb • Keep views lean • Business logic in: • Models • Services • Validation logic in forms
111. Danger
112. Domain pollution • When integrating with a 3rd party... • they will try and push their shortcomings into your platform
114. Anti-corruption layer Your platform Their platform Anti-corruption layer
115. Summary • Django e-commerce is an emerging force • Customising django apps isn’t easy • Oscar’s future: • NoSQL • Table inheritance
116. Image credits Books: http://www.flickr.com/photos/th3ph17/3091294342/ More books: http://www.flickr.com/photos/cheryl-j/3965942320/ Nail varnish: http://www.flickr.com/photos/greenzowie/5451402463/ Leather gloves: http://www.flickr.com/photos/theopenseas/175598276/ Lego shipping: http://www.flickr.com/photos/lydiashiningbrightly/5356210011/ Rubber gloves: http://www.flickr.com/photos/recyclethis/139373445/ Warehouse: http://www.flickr.com/photos/23748404@N00/15648677/ Taxonomy: http://www.flickr.com/photos/kqedquest/831547339/ T-shirts: http://www.flickr.com/photos/blazerman/177165473/