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The March To 3
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daniellindsley
April 08, 2013
Technology
1
120
The March To 3
The How's and Why's of porting to Python 3.
daniellindsley
April 08, 2013
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Transcript
The March To3
Who? • Daniel Lindsley • Pythonista since 2003 • Djangonaut
since 2006 • Author of Tastypie / Haystack / itty / others
None
Your language is...
Your language is... DEAD
Your language is... DEAD ...for small values of “dead”.
None
None
⦸
None
None
⦸
None
is dead;
is dead; Long live !
None
Why port to Python 3?
Active Development Python 2.7.x will only get security updates. No
Python 2.8 ever.
As Fast As 2.7 With 3.3 & it’ll only get
better.
Cleaned Up Syntax We’ll get to some of these in
a bit.
Better String Handling Unicode everywhere.
Stable
None
Changes from 2 to 3 •Removals • Backticks, classic classes
• <>, apply, reduce, dict.has_key • Others
Changes from 2 to 3 •Changed • print is now
print() • next() is now __next__() • Better raise syntax • Metaclasses
Changes from 2 to 3 •Changed (cont.) • Faster Decimal
implementation • Reorganized & spruced up stdlib • Careful with I/O!
Changes from 2 to 3 •New! • Built-in OrderedDict •
String formatting • dict / set comprehensions • Generator delegation via yield from
Changes from 2 to 3 •New! (cont.) • Built-in virtualenv
support! • unittest2 by default! • World domination with importlib
None
“What versions should I support?”
“What versions should I support?” Simple answer: Python 2.6+ &
Python 3.3+
None
“So how do I port?”
IT DEPENDS!
Decide between... • A One-time port • A Combined 2
& 3 codebase ...or...
None
The One-time port
The One-time port • Ensure you have good test coverage
• Use 2to3 to convert the codebase • Run tests & fix until it passes
None
The Combined 2 & 3 codebase
The Combined 2 & 3 codebase • First, you need
a venv: •virtualenv -p python3 env3 •. env3/bin/activate
The Combined 2 & 3 codebase • Ensure you have
good test coverage • Require six as a dependency • Use six to patch over the differences • Run tests in Py3 & fix until it passes... • ...then run tests in Py2 & fix until it passes!
None
Using six in practice
Demo time.
None
More information • http://pyvideo.org/video/1730/python-33- trust-me-its-better-than-27 • http://pyvideo.org/video/1787/porting- django-apps-to-python-3 • http://pyvideo.org/video/1704/why-you-
should-use-python-3-for-text-processing • http://pythonhosted.org/six/
More information • http://www.dabeaz.com/python3io/ MasteringIO.pdf
Thanks! @daniellindsley https://github.com/toastdriven