Porting Django apps to Python 3

Presented at DjangoCon AU 2013.

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.” — http://django.me/1.5 “As of Django 1.6, Python 3 support is considered stable and you can safely use it in production. — http://django.me/faq
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* ? Oracle
9. ✓ modwsgi ✓ uWSGI ✓ gunicorn: sync ? gunicorn: async
10. ✓ South ✓ Celery ✓ Raven (Sentry) ✓ django-extensions ✘ django-compressor ✘ django-social-auth ✘ django-tagging ✘ django-debug-toolbar ✘ django-registration ✘ Haystack
11. ✓ South ✓ Celery ✓ Raven (Sentry) ✓ django-extensions ✓ django-pipeline ✓ django-allauth ✓ django-taggit ✘ django-debug-toolbar ✘ django-registration ✘ Haystack
12. Should I use Python 3?
13. Options 1. Python 3 only. 2. Translated source (2to3). 3. Single codebase.
14. Python 3 only?
15. 2to3
16. ˑ Single source wins!
17. HOWTO
18. 1. Choose an approach
19. 2. Evaluate dependencies
20. 3. Get the test suite running
21. 4. Fix unicode handling
22. 5. Iterate on test failures
23. Case study: a new website
24. 1. Choose an approach Single source: Python 3.3 only.
25. 2. Evaluate dependencies • Light CMS capabilities. • Moderately complex user / permissions / authentication system. • Heavy integration with social networks. • Moderate traffic with extreme “spikes.”
26. 3. Get the test suite running ✓ django-discover-runner
27. 4. Fix unicode handling django.utils.encoding
28. ˑIt works! ... but costs ~20% more.
29. Case study: django-sitetree Ported by Jeff Triplett (@webology) https://github.com/idlesign/django-sitetree/commit/c7475
30. 1. Choose an approach Shared source: Python 2.6+, 3.3; Django 1.4+
31. 2. Evaluate dependencies None (whew).
32. 3. Get the test suite running Tox: http://tox.readthedocs.org/
33. Tox [tox] envlist  -­‐  py27-­‐django14,  py33-­‐django15 [py27-­‐django14] basepython  =  python2.7 deps  =  Django==1.4 [py33-­‐django15] basepython  =  python33 deps  =  Django==1.5
34. 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
35. 4. Fix unicode handling django.utils.encoding
36. 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
37. 5. Iterate on test failures Six: http://pythonhosted.org/six/ (also django.utils.six)
38. Six class  C:                                    class  C(metaclass=M)      __metaclass__  =  M class  C(six.with_metaclass(M)): 2 3
39. 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
40. Six if  six.PY3: ...
41. More info: django.me/py3
42. ˑ We’ve done our job…
43. ˑ We’ve done our job… now it’s your turn!
44. Thanks! Jacob Kaplan-Moss jacob@jacobian.org