in brief Python has left its compatibility chains in the past with the release of version 3.0 of the popular dynamic language.
The release notes on Python.org describe the new version of the language as being mostly the same, but many details have changed considerably, and a lot of deprecated features have finally been removed. Python 3.0 is incompatible with previous versions of the language.
Over the extended lead up to the release, Python incorporated some 3.0 features in new versions of the Python 2.x line.
A list of new features is available from Python.org, but the new version’s performance is 10 per cent slower than its 2.x brethren.