Porting Django apps to Python 3

Transcript

1. Porting Django apps to Python 3 Jacob Kaplan-Moss jacob@jacobian.org

2. “Django 1.5 is… the first release with Python 3 support!

   ... Everything’s in place for you to start porting your apps to Python 3.” — https://docs.djangoproject.com/en/1.5/releases/1.5/

3. Do I want to use Python 3?

4. ˑYes!

5. Python 3: now with 30% fewer warts!

6. ˑ Unicode no longer sucks!

7. Can I use Python 3?

8. ✓ SQLite ✓ PostgreSQL ✘ MySQL

9. ✓ modwsgi ✓ uWSGI ✓ gunicorn: sync ✘ gunicorn: async

10. ✓ South ✓ Celery ✓ django-pipeline ✘ django-debug-toolbar ✘ django-registration

    ✘ django-extensions ✘ Haystack ✘ django-tagging ✘ Sentry ✘ django-compressor

11. Should I use Python 3?

12. Options 1. Python 3 only. 2. Translated source (2to3). 3.

    Single codebase.

13. Python 3 only?

14. 2to3

15. ˑ Single source wins!

16. HOWTO

17. 1. Choose an approach

18. 2. Evaluate dependencies

19. 3. Get the test suite running

20. 4. Fix unicode handling

21. 5. Iterate on test failures

22. Case study: a new website

23. 1. Choose an approach Single source: Python 3.3 only.

24. 2. Evaluate dependencies • Light CMS capabilities. • Moderately complex

    user / permissions / authentication system. • Heavy integration with social networks. • Moderate traffic with extreme “spikes.”

25. 3. Get the test suite running ✓ django-discover-runner

26. 4. Fix unicode handling django.utils.encoding

27. ˑIt works! ... but costs ~20% more.

28. Case study: django-sitetree Ported by Jeff Triplett (@webology) https://github.com/idlesign/django-sitetree/commit/c7475

29. 1. Choose an approach Shared source: Python 2.6+, 3.3; Django

    1.4+

30. 2. Evaluate dependencies None (whew).

31. 3. Get the test suite running Tox: http://tox.readthedocs.org/

32. Tox [tox] envlist  -­‐  py27-­‐django14,  py33-­‐django15 [py27-­‐django14] basepython  =  python2.7

    deps  =  Django==1.4 [py33-­‐django15] basepython  =  python33 deps  =  Django==1.5

33. Syntax changes print  "foo"   print("foo") except  Exception,  ex:  

    except  Exception  as  ex: raise  Exception,  "msg"        raise  Exception("message”) class  C:                                    class  C(metaclass=M)      __metaclass__  =  M More: http://docs.python.org/3.0/whatsnew/3.0.html 2 3

34. 4. Fix unicode handling django.utils.encoding

35. Models and unicode class  M(models.Model):   class  M(models.Model):    

       def  __unicode__(self):            def  __str__(self):                return  self.name                  return  self.name @python_2_unicode_compat class  M(models.Model):        def  __str__(self):                return  self.name 2 3

36. 5. Iterate on test failures Six: http://pythonhosted.org/six/ (also django.utils.six)

37. Six class  C:              

                         class  C(metaclass=M)      __metaclass__  =  M class  C(six.with_metaclass(M)): 2 3

38. Six isinstance(s,  str)   isinstance(s,  bytes) isinstance(s,  unicode)   isinstance(s,

     str) isinstance(s,  six.binary_type) isinstance(s,  six.text_type) 2 3

39. Six if  six.PY3: ...

40. ˑ django.me/py3 is your new bicycle

41. Thanks! Jacob Kaplan-Moss jacob@jacobian.org Questions? Follow me to room 201!