switch to python 3…now…immediately

Copyright © 2013 Russel Winder 1

Switch to Python 3…Now…

Immediately!

Prof Russel Winder

http://www.russel.org.uk

email: [email protected]: [email protected]

twitter: @russel_winder

mailto:[email protected]


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polemic noun a strong verbal or written attack on someone or something


Introduction


2.72.62.5

2.4

2.3

2.2


3.33.2

3.13.0


gs/2\../3.3/g


So what's the problem?

● Python 2 remains the default Python.● Too many people and organizations are far too

afraid of change.

Why do people and organizationsbecome so afraid of change?


So what's the solution?

● Python Software Foundation (PSF) should declare Python 3 the default Python immediately.

People and organizations can implement this now:python python2→

replaced by:python python3→


But…world, we have a problem…

● …a few influential organizations are telling people not to use Python 3 but to stay with Python 2, and…

● …some crucial projects can't or won't get Python 3 versions out.

Many projects are now both Python 2 andPython 3 or getting there very rapidly.

Afraid of change?

Afraid of change?


Recalcitrant organizations and projects

should just pull their fingers out and

set Python 3 as their standard.


Or at least ensure their codebases

run under both Python 2 and Python 3.


Being Python 2 and 3 compatible

● 2to3 not useful, its a one shot transform tool.● six package might be useful in parts, and/or…● …modernize package might help, but…● …is manual the best?


Embrace

managed and controlled

change.


Be agile.


Justifications


Python 2 is a dead end.

Python 3 is the developing future.


print(x)

exec(x)


from __future__ import print_function


from __future__ import ( division, absolute_import, print_function, unicode_literals,)


x = [x * x for x in range(100) if x % 10 == 0]


x = {x * x for x in range(100) if x % 10 == 0}


x = {x: x * x for x in range(100) if x % 10 == 0}


Sadly (!) Python 2.7 is getting

backports of things from Python 3.


Fortunately Python 2.6

and earlier are not.


Python 2 is strict,

Python 3 is (sort of) lazy


map(lambda x: x * x, filter(lambda x: x % 10 == 0, range(100))


range(x)

xrange(x)

tuple(range(x))

range(x)→


Not Sequences, but Iterators

items

keys

values

iteritems

iterkeys

itervalues

items

keys

values

→


Competition


Python is under challenge

● Go is taking over from Python for many people.● Native, not interpreted.● Solid concurrency model – CSP

● D is hoping to take over from C, C++, Go, Python.● Native, not interpreted.● Solid concurrency models – actors, data parallelism


Native code languages are now

as expressive as Python.


And native code programs are

way, way faster than Python programs.


Statically compiled languages catch errors at

compile time that are horrendous run

time bugs in dynamic languages.


Are you concurrent?

● Who's using thread?● Who's using threading?


Are you parallel?

● Who's using thread?● Who's using threading?● Who's using multiprocessing?


At least IronPython and Jython

do not have a GIL as

CPython and PyPy do.


Support the PyPy STM/AME experiment.

http://www.pypy.org/tmdonate.html


ActorsIndependent processes communicating via asynchronous exchange of messages

CSPSequential processes connected by channels using synchronous message exchange (rendezvous).

DataflowOperators connected by channels with activity triggered by arrival of data on the channels.


ActorsIndependent processes communicating via asynchronous exchange of messages


DataflowOperators connected by channels with activity triggered by arrival of data on the channels.


CSPSequential processes connected by channels using synchronous message exchange (rendezvous).


Data ParallelismTransform a sequence to another sequence where all individual actions happen at the same time.


Futures are the future.


Along with process pools

and thread pools.


Concurrent.futures

● Python 3.2 package to abstract over threads and processes to give an asynchronous function call and future system.

cf. futures package for Python 2.

http://pypi.python.org/pypi/futures


Talking of PyPy…

http://www.pypy.org/


Support PyPy for Python 3.

http://www.pypy.org/py3donate.html


Conclusion


There are no real reasons

to stay with Python 2…


…so Python 3 should be

Considered mandatory.


Challenge


Problem

Python 3Python 2

Is there a problem, the solution to which canbe coded in Python 2, but not better in Python 3?


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Switch to Python 3…Now…

Immediately!

Prof Russel Winder

http://www.russel.org.uk

email: [email protected]: [email protected]

twitter: @russel_winder

mailto:[email protected]

switch to python 3…now…immediately

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