&quot;There was exactly one breaking point, from Python 2 to Python 3&quot;<p>One breaking point?<p>The majority of the libraries that I use don&#x27;t even work properly in Python 3.  The standard Mysql library for instance, which is used in the majority of ORMs (including SQLalchemy) isn&#x27;t included in Python 3, which means you need to make major changes&#x2F;try to use a different library.<p>The case of many standard libraries were changed, breaking lots of code.  Example: ConfigParser to configparser.<p>Even simple things like print &#x27;test&#x27; is now print(&#x27;test&#x27;)<p>These are only a few examples.  There are lots of other major changes that break 2.X code.<p>I have been using Python 2.X for all of my projects and wanted so badly to change to 3.x for my new projects.  However, because of all incompatibilities, I can&#x27;t.<p>I don&#x27;t think I&#x27;m alone on this either.  Python 3.X still isn&#x27;t being used by the majority of developers.