Python 3.0 (2008)
Python 3.0 broke backward compatibility with Python 2, changing print statements to functions and making strings Unicode by default. The transition took over a decade as the community slowly migrated.
Many projects stayed on Python 2 for years, slowing adoption of the new version.
Python 3 became the standard, and Python 2 was retired in 2020.
Python 3.15's UTF-8 default continues the text-handling reforms that began with Python 3.0, but with far less disruption.
