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Transcript 
3
Armin Ronacher
http://lucumr.pocoo.org/ // [email protected] // http://twitter.com/mitsuhiko
About Me
•using Python since version 2.2
•not-a-committer-with-commit-rights!?
•Part of the Pocoo Team: Jinja,
Werkzeug, Sphinx, Zine, Flask
A little bit of History
1991
Python Appears
‣
‣
‣
Exceptions
Multiple Inheritance
C inspired IO system
1995
Python 1.5
‣
‣
‣
‣
Regular Expressions
Exceptions are Classes
Built in Package Support
It can be embedded!
Python 2.0!
‣
‣
‣
‣
‣
2000
Spoiler: this is where it gets interesting
Unicode Support
Augmented assignments (+=, -= etc.)
List Comprehensions
Garbage Collector
Python Enhancement Proposals!
Footnote: some of this was in 1.6 already
2004
Python 2.4!
Spoiler: unicode becomes interesting
‣
‣
‣
‣
‣
Source Encoding
Boolean Type (True/False)
sets
reverse iteration
generator expressions
Footnote: some of this was in 2.3 already
Not all is Fine
String Coercion
It’s bytes — it’s charpoints
!!!!"!#!$%&'&($
!!!!)!#!*$+,()&-$
!!!!$."--/!$!0!"
1."--/!%&'&(1
!!!!$."--/!$!0!)
*1."--/!+23&4()&-1
!!!!5(67'!8
."--/!+,()&-
String Coercion [fail]
It’s an exception
!!!!"!#!*$%&'&($
!!!!)!#!$+,()&-$
"#$%&'$%()9:/;'!(&<&7'!<"--!-";'=*
))>>>
+,-%./&0&%./&1##.#*)?6))&(6;@
Print is a Statement
why is that?
!!!!5(67'!$.&--/$A!4B
.&--/!4B
!!!!5(67'9$.&--/$A!4B=
91.&--/1A!4B=
!!!!3!#!5(67'
"#$%&'$%()9:/;'!(&<&7'!<"--!-";'=*
))>>>
23,4$51##.#*)67C"-6D!;E7'"3
O HAI — IM TEH ITERATOR
… and I want my place
!!!!"!#!F1G//1H!IA!1)"(1H!BJ
!!!!">K&E;9=
L1G//1A!1)"(1M
!!!!">6'&(K&E;9=
ND6<'6/7"(EOK&E6'&("'/(!/)P&<'!>>>Q
Exceptions
let’s do some guessing
#$-6&!"
#$-6&!"A!)A!<
#$-6&!99"A!)=A!<=A!D
&5%&74!RH
&5%&74!RA!+H
&5%&74!9RA!+=A!SH
Exceptions improved
that should clear it up:
#$-6&!"
#$-6&!)>T6'@8'("<&)"<K9<=
#$-6&!99"A!)=A!<=A!D
&5%&74!RH
&5%&74!R!$6!+H
&5%&74!9RA!+=!$6!SH
New Stuff in 3.x
non-local names
Re-bind variables from outer scopes:
/&8!:"K&8</*7'&(9676'6"-#U=H
!!!!C"-!#!676'6"!!!!/&8!67<9=H
!!!!!!!!,.,9.%$9!C"!!!!!!!!(C!#!C"!!!!!!!!C"-!0#!I
!!!!!!!!#&4:#,!(C
!!!!#&4:#,!67<
New Literals
Set Literal
!!!!"!#!FIA!BA!VJ
!!!!)!#!;&'9=
Footnote: there is no literal for an empty set
Extended Unpacking
Unpack in variables
!!!!G6(;'A!;&</7DA!W(&;'!#!*75"<K9=
Footnote: The rest is a list with all the unassigned items
Abstract Base Classes
Duck Typing Improved
!!!!%9$66!XEY'&("'/(9/)P&<'=H
;;;!!!!/&8!887&3'889;&-G=H
;;;!!!!!!!!#$-6&!Z'/5Y'&("'6/79=
;;;!!!!/&8!886'&(889;&-G=H
;;;!!!!!!!!#&4:#,!;&-G
;;;
!!!!8#.<!</--&<'6/7;!-<7.#4!Y'&("'/(
!!!!6;67;'"7<&9XEY'&("'/(9=A!Y'&("'/(=
[(*&
Footnote: Implicit subclasses, awesome!
Annotations!
Add type information to your signatures
8#.<!7*:)&(;!-<7.#4!\*:)&(
/&8!"DD9"H!\*:)&(A!)H!\*:)&(=!OQ!\*:)&(
!!!!#&4:#,!"!0!)
Footnote: These are unchecked, Sphinx can use them
Goodies
print a function, super with magic
!!!!"!#!5(67'
!!!!"94B=
4B
!!!!%9$66!["?Z&'9;&'=H
;;;!!!!!/&8!"DD9;&-GA!'"?=H
;;;!!!!!!!!!;*5&(9=>"DD9'"?>-/T&(9==
;;;
!!!!'E5&9675*'9==
.&--/!]/(-D^
N'E5&!_;'(`Q
Brrr: How does super() work? You don’t wanna know
New Land
Backwards Incompatible
be courageous
‣
‣
‣
Break up with the Past
Fix the issues
Help the transition with automation
Side By Side
how can we do that?
‣
Python 3.x and Python 2.x are
developed side by side
‣
Python 2.x slowly adopts features that
come from 3.x or make the automated
conversion easier
Automation
2to3 for the rescue
‣
A tool to convert from Python 2.x
sources to 3.x
‣
Operates on the parsing-time
information only.
‣
Not 100% correct, but close
There Be Dragons
Step by Step
Library or Application?
‣
‣
‣
2to3 caters for both
But the experience differs
generally: application easier
#1
Step by Step
Unicode or Bytes?
‣
‣
‣
did your API use bytes?
did it use unicode?
what should it use now?
#2
Step by Step
#3
Are you sure?
‣
‣
‣
Beware of the stdlib
things unicodified along the way
explicit encoding!
Step by Step
#4
Adapt to new idioms
‣
‣
str.format instead of %
‣
‣
abstract base classes
keys() and not iterkeys(), beware on
custom classes
the new IO system
Step by Step
Port your Tests
‣
‣
‣
Make sure the tests run on 3.x
Get rid of your doctests. Now!
make sure 2to3 only has to correct
syntax, not semantics. Runtime
checks.
#5
2to3 will byte you
Unicode Breakage
Affects many 2.x libraries
‣
‣
‣
‣
class implements ==:,-%./&==
and ==64#== calls into ==:,-%./&==
on 3.x: RuntimeError
Can be fixed with a custom fixer
Preprocessing
If everything else fails …
‣
‣
write a preprocessor
monkey-patch yourself in
-8!;E;>C&(;6/7867G/!Q#!9VA!U=H
!!!!8#.<!5(&5(/<&;;/(!-<7.#4!(&G"<'/(8;'(67?
!!!!8#.<!-6)B'/V>(&G"<'/(!-<7.#4!a&G"<'/(67?[//!!!!a&G"<'/(67?[//->(&G"<'/(8;'(67?!#!(&G"<'/(8;'(67?
Footnote: that’s what SQLAlchemy does
Changing Protocols
What if you depend on something?
‣
‣
WSGI changes and is broken right now
web applications are an unrealistic
target for the time being.
Rejoice: WSGI 1.1 is coming around
Fixing with Fixers
What are Fixers?
2to3 does not work at runtime
‣
‣
‣
‣
2to3 is guessing
has certain assumptions of your code
fixers operate on a parse tree
fixers can refactor and modify code
Anatomy of a Fixer
A fixer to rename functions
8#.<!-6)B'/V!-<7.#4!G63&(8)";&
8#.<!-6)B'/V>G63&(8*'6-!-<7.#4!\":&A!+-"7Kb67&
%9$66!c63R-'d76</D&9!"#$%&'()$*+()$,"#=H
!!!!%R[[ea\!#!$$$
!!!!G*7<#G*7<D&GN!1D&G1!7":&#188*76</D&881
!!!!!!!!!!!!!!!!!!5"(":&'&(;N!191!\RXe!1=1!Q!"7E0!Q
!!!!$$$
!!!!/&8!'("7;G/(:9)$-!A!7/D&A!(&;*-';=H
!!!!!!!!7":&!#!(&;*-';L17":&1M
!!!!!!!!7":&>(&5-"<&9\":&9188;'(881A!5(&G63#7":&>5(&G63==
Running custom Fixers
use distribute!
‣
‣
‣
distribute replaces setuptools
has builtin 2to3 support
the distribution system for 3.x
distribute: http://pypi.python.org/pypi/distribute
Hook into distribute
add this to your setup.py
&3'("!#!FJ
-8!;E;>C&(;6/7867G/!Q#!9VA!U=H
!!!!&3'(">*5D"'&9
!!!!!!!!*;&8B'/V#[(*&A
!!!!!!!!*;&8B'/V8G63&(;#L1<*;'/:8G63&(;1M
!!!!=
;&'*59>>>A!WW&3'("=
distribute: http://pypi.python.org/pypi/distribute
Porting Jinja2
What is it?
‣
‣
‣
Jinja2 — a template engine
Codebase: 10KLOC
In 2.x unicode based
Porting Jinja2
Porting Experience?
‣
‣
‣
# custom fixers: 3
preprocessing? nope
passing tests? all!
documentation)
(except for doctests in the
Porting Jinja2
An Example Fixer
8#.<!-6)B'/V!-<7.#4!G63&(8)";&A!5E'(&&
8#.<!-6)B'/V>G63&(8*'6-!-<7.#4!\":&A!+-"7Kb67&A!\":&A!R''(A!R(?b6;'
%9$66!c63+(/K&7a&("6;67?9!"#$%&'()$*+()$,"#=H
!!!!%R[[ea\!#!$$$
!!!!("6;&8;':'N!1("6;&1!"7E!1A1!C"-#"7E!1A1!')#"7E!Q
!!!!$$$
!!!!f!(*7!)&G/(&!'@&!)(/K&7!B'/V!<@&<K&(!T6'@!'@&!;":&!?/"!!!!f!'(6&;!'/!(&T(6'&!6'!T6'@!"!(*-&!'@"'!D/&;!7/'!T/(K!/*'!G/(!P67P"
!!!!(*78/(D&(!#!I
!!!!/&8!'("7;G/(:9)$-!A!7/D&A!(&;*-';=H
!!!!!!!!')!#!(&;*-';L1')1M><-/7&9=
!!!!!!!!')>5(&G63!#!11
!!!!!!!!T6'@8')!#!R''(9(&;*-';L1C"-1M><-/7&9=A!\":&91T6'@8'("<&)"<K1==!0!2
!!!!!!!!!!!!!!!!!!LR(?b6;'9L')M=M
!!!!!!!!7&T!#!5E'(&&>\/D&9;&-G>;E:;>;6:5-&8;':'A!L\":&91("6;&1=M!0!T6'@8')=
!!!!!!!!7&T>5(&G63!#!7/D&>5(&G63
!!!!!!!!#&4:#,!7&T
Recipe
follow these steps for enlightenment
1) port doctests to unittest or your test suite
2) decide on your API for Python 3
3) check if 2to3 works on the tests
4) make the tests work
5) run 2to3 on your own code
6) add runtime fixes or custom fixers
Unladen Swallow
Unladen Swallow
Making Python Fast
1) LLVM JIT based
2) a development branch of Python
3) currently targeting 2.x, but major
changes will land in 3.x
Numbers
Current Status
Pystones
Plurk Profile
70
52.5
35
17.5
0
Python 2.5
Python 2.6
US Q1
US Q2
Current Status
Not very impressive
1) It’s not there yet
2) There will be a development branch
3) Python is hard to optimize, will take
some time
Ported Libraries
Ported Libraries
Web Related Libraries
‣
‣
‣
‣
‣
Jinja2
Mako
lxml
SQLAlchemy
httplib2
Ported Libraries
General Purpose
‣
‣
‣
‣
blinker
Pygments
PyYAML
tc [Tokio Cabinet]
Ported Libraries
Database / GUI
‣
‣
‣
sqlite3 [part of stdlib]
py-postgresql / pg8000-py3
PyQt
In The Pipeline
WSGI
‣
‣
‣
Werkzeug
CherryPy
mod_wsgi
Moving Target: WSGI 1.1 spec probably based on mod_wsgi for Python
Any Questions?
Legal
licensed under the creative commons attribution-noncommercialshare alike 3.0 austria license
© Copyright 2010 by Armin Ronacher
images in this presentation used under compatible creative commons
licenses. sources: http://www.flickr.com/photos/42311564@N00/2355590508/ http://www.flickr.com/photos/special/1597251/
http://www.flickr.com/photos/reillyandrew/2943521972/ http://www.flickr.com/photos/etobicokesouth/566912940/ http://
www.flickr.com/photos/azrasta/4528604334/ http://www.flickr.com/photos/oneeighteen/481873844/ http://www.flickr.com/photos/
mar00ned/260473163/ http://www.flickr.com/photos/revilla/1347710195/ http://www.flickr.com/photos/tommyhj/346075714/ http://
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nasedojp/2317015728/ http://www.flickr.com/photos/dullhunk/202872717/ http://www.flickr.com/photos/carbonnyc/3149965963/
http://www.flickr.com/photos/beezly/213880808/ http://www.flickr.com/photos/juniorvelo/4490511204/ http://www.flickr.com/photos/
niwota-studios/3586953497/ http://www.flickr.com/photos/the-lees/134610871/ http://www.flickr.com/photos/kubina/131673530/
http://www.flickr.com/photos/bootbearwdc/37621686/ http://www.flickr.com/photos/spursfan_ace/2328879637/ http://www.flickr.com/
photos/9619972@N08/1182211122/ http://www.flickr.com/photos/alanvernon/3659772103/ http://www.flickr.com/photos/jurvetson/
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