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Porting Django apps to Python 3
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Jacob Kaplan-Moss
March 16, 2013
Technology
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Porting Django apps to Python 3
PyCon 2013.
Jacob Kaplan-Moss
March 16, 2013
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Transcript
Porting Django apps to Python 3 Jacob Kaplan-Moss
[email protected]
“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/
Do I want to use Python 3?
ˑYes!
Python 3: now with 30% fewer warts!
ˑ Unicode no longer sucks!
Can I use Python 3?
✓ SQLite ✓ PostgreSQL ✘ MySQL
✓ modwsgi ✓ uWSGI ✓ gunicorn: sync ✘ gunicorn: async
✓ South ✓ Celery ✓ django-pipeline ✘ django-debug-toolbar ✘ django-registration
✘ django-extensions ✘ Haystack ✘ django-tagging ✘ Sentry ✘ django-compressor
Should I use Python 3?
Options 1. Python 3 only. 2. Translated source (2to3). 3.
Single codebase.
Python 3 only?
2to3
ˑ Single source wins!
HOWTO
1. Choose an approach
2. Evaluate dependencies
3. Get the test suite running
4. Fix unicode handling
5. Iterate on test failures
Case study: a new website
1. Choose an approach Single source: Python 3.3 only.
2. Evaluate dependencies • Light CMS capabilities. • Moderately complex
user / permissions / authentication system. • Heavy integration with social networks. • Moderate traffic with extreme “spikes.”
3. Get the test suite running ✓ django-discover-runner
4. Fix unicode handling django.utils.encoding
ˑIt works! ... but costs ~20% more.
Case study: django-sitetree Ported by Jeff Triplett (@webology) https://github.com/idlesign/django-sitetree/commit/c7475
1. Choose an approach Shared source: Python 2.6+, 3.3; Django
1.4+
2. Evaluate dependencies None (whew).
3. Get the test suite running Tox: http://tox.readthedocs.org/
Tox [tox] envlist -‐ py27-‐django14, py33-‐django15 [py27-‐django14] basepython = python2.7
deps = Django==1.4 [py33-‐django15] basepython = python33 deps = Django==1.5
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
4. Fix unicode handling django.utils.encoding
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
5. Iterate on test failures Six: http://pythonhosted.org/six/ (also django.utils.six)
Six class C:
class C(metaclass=M) __metaclass__ = M class C(six.with_metaclass(M)): 2 3
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
Six if six.PY3: ...
ˑ django.me/py3 is your new bicycle
Thanks! Jacob Kaplan-Moss
[email protected]
Questions? Follow me to room 201!