Porting Django apps to Python 3

PyCon 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.” — 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!