PyCon India: Snakes on the Web (2012)

Transcript

1. SNAKES ON THE WEB Jacob Kaplan-Moss [email protected] The history and

   future of Python on the web http://www.flickr.com/photos/kejhu/3751877257 2012

2. 㿄 http://jacobian.org/writing/snakes-on-the-web/

3. Web development SUCKS

4. How can I make it SUCK LESS?

5. None

6. 1. What sucks now?

7. 1. What sucks now? 2. How will we fix it?

8. 1. What sucks now? 2. How will we fix it?

   3. Can we fix it with Python?

9. http://www.flickr.com/photos/tonythemisfit/2904911703 In the beginning…

10. Hand-rolled HTML “The Stone Age” <h1>Appendix A: Model Definition Reference</h1>

    <p>Chapter 5 explains the basics of defining models, and we use them throughout the rest of the book. There is, however, a <em>huge</em> range of model options available not covered elsewhere. This appendix explains each possible model definition option.</p> <p>Note that although these APIs are considered stable, the Django developers consistently add new shortcuts and conveniences to the model definition. It&#8217;s a good idea to always check the latest documentation online at <a class="reference external" href="http://docs.djangoproject.com/">http://docs.djangoproject.com/</a>.</p> <div class="section" id="fields"> <h2>Fields</h2> <p>The most important part of a model &#8211; and the only required part of a model &#8211; is the list of database fields it defines.</p> <div class="admonition-field-name-restrictions admonition"> <p class="first admonition-title">Field Name Restrictions</p> <p>Django places only two restrictions on model field names:</p> <ol class="arabic"> <li><p class="first">A field name cannot be a Python reserved word, because that would result in a Python syntax error. For example:</p> <div class="highlight-python"><pre>class Example(models.Model): pass = models.IntegerField() # 'pass' is a reserved word!</pre> </div> </li> <li><p class="first">A field name cannot contain more than one underscore in a row, due to the way Django&#8217;s query lookup syntax works. For example:</p> <div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">Example</span><span class="p">(</ span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span> <span class="n">foo__bar</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span> <span class="c"># &#39;foo__bar&#39; has two underscores!</span> </pre></div> </div> </li> </ol> <p>These limitations can be worked around, though, because your field name doesn&#8217;t necessarily have to match your database column name. See &#8220;db_column&#8221;, below.</p> <p class="last">SQL reserved words, such as <tt class="docutils literal"><span class="pre">join</span></tt>, <tt class="docutils literal"><span class="pre">where</span></tt>, or <tt class="docutils literal"><span class="pre">select</span></tt>, <em>are</em> allowed as model field names, because Django escapes all database table names and column names in every underlying SQL query. It uses the quoting syntax of your particular database engine.</p> </div> <p>Each field in your model should be an instance of the appropriate <tt class="docutils literal"><span class="pre">Field</span></tt> class. Django uses the field class types to determine a few things:</p> <ul class="simple"> <li>The database column type (e.g., <tt class="docutils literal"><span class="pre">INTEGER</span></tt>, <tt class="docutils literal"><span class="pre">VARCHAR</span></tt>).</li> <li>The widget to use in Django&#8217;s forms and admin site, if you care to use it (e.g., <tt class="docutils literal"><span class="pre">&lt;input</span> <span class="pre">type=&quot;text&quot;&gt;</span></tt>, <tt class="docutils literal"><span class="pre">&lt;select&gt;</span></tt>).</li> <li>The minimal validation requirements, which are used in Django&#8217;s admin interface and by forms.</li> </ul> <p>A complete list of field classes follows, sorted alphabetically. Note that relationship fields (<tt class="docutils literal"><span class="pre">ForeignKey</span></tt>, etc.) are handled in the next section.</p>

11. SUCK. <h1>Appendix A: Model Definition Reference</h1> <p>Chapter 5 explains the

    basics of defining models, and we use them throughout the rest of the book. There is, however, a <em>huge</em> range of model options available not covered elsewhere. This appendix explains each possible model definition option.</p> <p>Note that although these APIs are considered stable, the Django developers consistently add new shortcuts and conveniences to the model definition. It&#8217;s a good idea to always check the latest documentation online at <a class="reference external" href="http://docs.djangoproject.com/">http://docs.djangoproject.com/</a>.</p> <div class="section" id="fields"> <h2>Fields</h2> <p>The most important part of a model &#8211; and the only required part of a model &#8211; is the list of database fields it defines.</p> <div class="admonition-field-name-restrictions admonition"> <p class="first admonition-title">Field Name Restrictions</p> <p>Django places only two restrictions on model field names:</p> <ol class="arabic"> <li><p class="first">A field name cannot be a Python reserved word, because that would result in a Python syntax error. For example:</p> <div class="highlight-python"><pre>class Example(models.Model): pass = models.IntegerField() # 'pass' is a reserved word!</pre> </div> </li> <li><p class="first">A field name cannot contain more than one underscore in a row, due to the way Django&#8217;s query lookup syntax works. For example:</p> <div class="highlight-python"><div class="highlight"><pre><span class="k">class</span> <span class="nc">Example</span><span class="p">(</ span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span> <span class="n">foo__bar</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span> <span class="c"># &#39;foo__bar&#39; has two underscores!</span> </pre></div> </div> </li> </ol> <p>These limitations can be worked around, though, because your field name doesn&#8217;t necessarily have to match your database column name. See &#8220;db_column&#8221;, below.</p> <p class="last">SQL reserved words, such as <tt class="docutils literal"><span class="pre">join</span></tt>, <tt class="docutils literal"><span class="pre">where</span></tt>, or <tt class="docutils literal"><span class="pre">select</span></tt>, <em>are</em> allowed as model field names, because Django escapes all database table names and column names in every underlying SQL query. It uses the quoting syntax of your particular database engine.</p> </div> <p>Each field in your model should be an instance of the appropriate <tt class="docutils literal"><span class="pre">Field</span></tt> class. Django uses the field class types to determine a few things:</p> <ul class="simple"> <li>The database column type (e.g., <tt class="docutils literal"><span class="pre">INTEGER</span></tt>, <tt class="docutils literal"><span class="pre">VARCHAR</span></tt>).</li> <li>The widget to use in Django&#8217;s forms and admin site, if you care to use it (e.g., <tt class="docutils literal"><span class="pre">&lt;input</span> <span class="pre">type=&quot;text&quot;&gt;</span></tt>, <tt class="docutils literal"><span class="pre">&lt;select&gt;</span></tt>).</li> <li>The minimal validation requirements, which are used in Django&#8217;s admin interface and by forms.</li> </ul> <p>A complete list of field classes follows, sorted alphabetically. Note that relationship fields (<tt class="docutils literal"><span class="pre">ForeignKey</span></tt>, etc.) are handled in the next section.</p>

12. CGI “The Bronze Age” use CGI; my $q = CGI->new;

    # Process an HTTP request @values = $q->param('form_field'); $fh = $q->upload('file_field'); $riddle = $query->cookie('riddle_name'); %answers = $query->cookie('answers'); # Prepare various HTTP responses print $q->header(); print $q->header('application/json'); $cookie1 = $q->cookie(-name=>'riddle_name', -value=>"The Sphynx's Question"); $cookie2 = $q->cookie(-name=>'answers', -value=>\%answers); print $q->header( -type => 'image/gif', -expires => '+3d', -cookie => [$cookie1,$cookie2] ); print $q->redirect('http://somewhere.else/in/movie/land');

13. SUCK. use CGI; my $q = CGI->new; # Process an

    HTTP request @values = $q->param('form_field'); $fh = $q->upload('file_field'); $riddle = $query->cookie('riddle_name'); %answers = $query->cookie('answers'); # Prepare various HTTP responses print $q->header(); print $q->header('application/json'); $cookie1 = $q->cookie(-name=>'riddle_name', -value=>"The Sphynx's Question"); $cookie2 = $q->cookie(-name=>'answers', -value=>\%answers); print $q->header( -type => 'image/gif', -expires => '+3d', -cookie => [$cookie1,$cookie2] ); print $q->redirect('http://somewhere.else/in/movie/land');

14. PHP “The Iron Age”

15. Same idea, (slightly) better tech. http://www.flickr.com/photos/jerhoyet/2377140741

16. http://www.flickr.com/photos/just_jump/2972461681 Page-oriented

17. Rdio.app

18. Frameworks “The Industrial Revolution”

19. None

20. The modern web framework:

21. http://www.flickr.com/photos/nikonvscanon/2128705916 High-level

22. http://www.flickr.com/photos/joelaz/2868356069 Application-oriented

23. http://www.flickr.com/photos/ppdigital/2329405081/ Large blocks

24. http://www.flickr.com/photos/jasephotos/2913135232/ Rapid development

25. None

26. http://www.flickr.com/photos/nattu/1190083977 Fun!

27. What comes NEXT?

28. What problems SUCK NOW?

29. Interoperability SUCKS.

30. http://www.flickr.com/photos/amberandclint/3266859324/ Frameworks: good

31. Lock-in: bad! http://www.flickr.com/photos/striatic/2191404675/

32. Rule 1: Don’t piss off your users.

33. Software becomes domain-specific.

34. Cede control gracefully. http://www.flickr.com/photos/aidan_jones/3575000735

35. http://www.flickr.com/photos/kpwerker/421386062/ Fram ew ork inter-op

36. We CAN find areas in common

37. Rich applications SUCK.

38. HTML 5

39. The best thing to happen to WEB FRAMEWORKS?

40. http://www.flickr.com/photos/oskay/156280584/ Current frameworks don’t fit.

41. “Real-time”

42. None
43. None
44. None

45. This is the future.

46. Is real-time possible in PYTHON?

47. Yes! But. https://github.com/ptone/django-live

48. Traditional Django app

49. Real-time Django REDIS SOCKET IO GEVENT BACKBONE

50. Django

51. Django 750 lines of code

52. Django 750 lines of code 18 external libraries

53. Django 750 lines of code 18 external libraries 4 running

    services

54. Django 750 lines of code 18 external libraries 4 running

    services Meteor

55. Django 750 lines of code 18 external libraries 4 running

    services Meteor 12 lines of code

56. Django 750 lines of code 18 external libraries 4 running

    services Meteor 12 lines of code 0 external libraries

57. Django 750 lines of code 18 external libraries 4 running

    services Meteor 12 lines of code 0 external libraries 1 running service

58. Is real-time possible in PYTHON?

59. Is real-time EASY in Python?

60. Concurrency SUCKS.

61. http://www.flickr.com/photos/marc_buehler/3053243413 All roads lead to multi-core

62. Sparc T4

63. 256 hardware threads

64. None

65. TWISTED & TORNADO & GEVENT & EVENTLET & ...

66. Actors STM PDS Dataflow Threads Events Tuple spaces Ted Leung,

    A survey of concurrency constructs: http://tinyurl.com/mmbqe6

67. Help!

68. 2020

69. I want to be using PYTHON!

70. “ ” Good software takes ten years. Get used to

    it. — Joel Spolsky http://tinyurl.com/ca4pr

71. So we need to START NOW!

72. THANK YOU! Jacob Kaplan-Moss [email protected] http://www.flickr.com/photos/kejhu/3751877257