Python 3 - What is new, what's changed and why

Python module Y300

Exercises, examples and other material relating to training module Y300. This topic is presented on public courses Learning to program in Python, Python Programming, Intermediate Python

Background

Python originated in 1988, and there are some elements dating back to the early days which will hold back the ongoing development and use of the language 30 years later in today's very different world. In Python 3, some of these time-expired features have been replaced by more currently appropriate facilities, yet in a way that code may be moved across with as little pain as possible. While much development work continues in Python 2, courses continue to cover that version, but always with Python 3 in mind so that our delegates are writing code that's good for the future too.

Articles and tips on this subject		updated
2871	Moving from Python 2.6 to Python 3 When should you move your development to Python 3? When you're good and ready and you're certain that you'll not need to run your code on Python 2 again. Up to that point, the 2to3 utility will convert code for you. Here's an example where I converted a short example script called "london" - using ...	2010-07-14
2778	Learning to program in Python 2 ... and / or in Python 3 Yesterday - "Learning to Program in Python" - and I'm now teaching the day so that it's both Python 2 and Python 3 compatible. But it's really an intro day, and we'll vary how we go for the following 3 days of the course, majoring in an appropriate direction for our group - that's a luxury we have when ...	2010-05-25
2559	Moving the product forward - ours, and MySQL, Perl, PHP and Python too I have just posted a "steady as she goes" message, welcoming the new decade but reassuring our customers that we're carrying on offering very much the same high quality courses, and the same high quality hotel rooms. But things can't stand totally still - they would stagnate, courses would get out ...	2010-01-01
2285	Great new diagrams for our notes ... Python releases When training, I project onto a white wall ... and I draw onto the projected image, and add extra notes and diagrams around the side too - after all, the whole wall is a whiteboard. Some of the diagrams and slides that I'll come up with are new / unique for an individual course, and I end up photographing ...	2009-07-13
2277	Python classes / courses - what version do we train on? Usually, the release number of a programming language that's used on a 'first level' course doesn't make a big difference as the changes tend to be quite minor - after all, languages cannot change much for who would develop e piece of code using a syntax that was likely to go out of date? But that's ...	2009-07-11
1791	The road ahead - Python 3 A couple of days ago, I mentioned Python 3 in general terms - and today I'm starting to flesh out the road ahead. print The print operator in Python was always a bit curious, with the trailing comma to signify "no new line" ... and that has been replaced by a print function, with named parameters ...	2008-09-11
1788	Python 2 to Python 3 / Python 3000 / Py3k There's a new release of Python on the horizon. Well - it's rather closer than the horizon, as there are beta test releases around, and a final production release is due within the month. It has been known as Python 3000 and Py3k along the way - but the release is numbered 3.0 and it's really known ...	2008-09-11
753	Python 3000 - the next generation There is no definite schedule for Python 3 (a.k.a. Python 3000 or Py3K) but a Python Enhancement Proposal (PEP) that details plans exists. There's a guiding principle to reduce duplication by removing old ways of doing things which will break version 2 compatibility. (Heard it before ... Perl 5 to Perl ...	2006-06-09

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Examples from our training material

george	Integer v float arithmetic
git_2.py	Generator and xrange - Python 2
git_3.py	Generator in Python 3, range replaces xrange
input_2.py	inputs in Python 2
input_3.py	Inputs in Python 3 - input replaces raw_input
john	input and raw_input - Python 2 and Python 3
london.2	Python 2.6 for conversion to Python 3
london.3	Python 3 - converted from Python 2.6 example
print_2.py	print in python 2
print_3.py	print in Python 3 - print now a function

Background information

Some modules are available for download as a sample of our material or under an Open Training Notes License for free download from http://www.training-notes.co.uk.

Topics covered in this module

Introduction.
Why Python 3?
Print as a function.
Input changes.
Range and other iterators (map, etc).
nonlocal (compared to global).
New style classes.
Strings, bytes, unicode and string formatting.
Exceptions.
Other changes
A note on Decorators.
Versions 2.6 and 2.7 3.0 to 3.3 and 2to3
A Strategy for upgrade.

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