Python 3.0 upgrade incompatible with earlier versions

The Python Software Foundation is working concurrently on two upgrades to the core language and anticipates most people will stick with the Python 2 line for years

Python 3.0, a new version of the language released earlier this week, has incompatibilities with the 2.x line, according to the Python Software Foundation.

While saying the language is mostly the same, the foundation said details such as how built-in objects like dictionaries and strings work "have changed considerably and a lot of deprecated features have finally been removed." The standard library also has been reorganized to make it more accessible and discoverable.

Python vs. PHP: Choosing your next project's language

In a blog posting on Thursday, Guido van Rossum, lead developer of Python, called the 3.0 release "the first ever intentionally backwards incompatible Python release."

"There are more changes than in a typical release, and more that are important for all Python users. Nevertheless, after digesting the changes, you'll find that Python really hasn't changed all that much -- by and large, we're mostly fixing well-known annoyances and warts, and removing a lot of old cruft," van Rossum said.

Interviewed Friday morning, foundation representative David Goodger said "We fixed problems so we can go forward and add features more easily in the future without having to work around previous bad decisions."

A transitional release toward the 3.0 platform, Python 2.6, was released in October and updated with bug fixes in Python 2.6.1 this week. A Python 2.7 release also is planned, and the foundation anticipates most people will stick with the Python 2 line for years, Goodger said.

First released in 1991, Python is a general purpose language that has been popular in Web development. Among the new features in Python 3.0 are simplified rules for ordering comparisons, replacement of the print statement with a print function, and use of views and iterators instead of lists. Syntactic changes also have been made.

Python 3.0 uses concepts of text and binary data instead of Unicode strings and 8-bit strings. Text is Unicode but encoded Unicode is represented as binary data.

"As a consequence of this change in philosophy, pretty much all code that uses Unicode, encodings, or binary data most likely has to change," according to the foundation. But the change is for the better, the foundation said. With Python 3.0, the default way to handle text is to use Unicode throughout, Goodger said.

Featured with Python 2.6 is a tool called 2to3, to translate Python 2.6 code to Python 3.0. That tool will be improved along with the Python 2 line, Goodger said.

Python 3.0 is downloadable here.

Join the newsletter!


Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.

Tags python

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Paul Krill

Show Comments

Cool Tech

Toys for Boys

Family Friendly

Stocking Stuffer

SmartLens - Clip on Phone Camera Lens Set of 3

Learn more >

Christmas Gift Guide

Click for more ›

Brand Post

Most Popular Reviews

Latest Articles


PCW Evaluation Team

Michael Hargreaves

Microsoft Office 365/Dell XPS 15 2-in-1

I’d recommend a Dell XPS 15 2-in-1 and the new Windows 10 to anyone who needs to get serious work done (before you kick back on your couch with your favourite Netflix show.)

Maryellen Rose George

Brother PT-P750W

It’s useful for office tasks as well as pragmatic labelling of equipment and storage – just don’t get too excited and label everything in sight!

Cathy Giles

Brother MFC-L8900CDW

The Brother MFC-L8900CDW is an absolute stand out. I struggle to fault it.

Luke Hill


I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Featured Content

Product Launch Showcase

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?