Title: Theory / Unimportant / CS / Programming / Python / PEP / 5 Guidelines for Language Evolution

Question: Steps For Introducing Backwards-Incompatible Features
Answer: Propose backwards-incompatible behavior in a PEP. The PEP must include a section on backwards compatibility that describes in detail a plan to complete the remainder of these steps.
Page: https://www.python.org/dev/peps/pep-0005/
Answer2: Once the PEP is accepted as a productive direction, implement an alternate way to accomplish the task previously provided by the feature that is being removed or changed. For instance if the addition operator were scheduled for removal, a new version of Python could implement an "add()" built-in function.
Answer3: Formally deprecate the obsolete construct in the Python documentation.
Answer4: Add an optional warning mode to the parser that will inform users when the deprecated construct is used. In other words, all programs that will behave differently in the future must trigger warnings in this mode. Compile-time warnings are preferable to runtime warnings. The warning messages should steer people from the deprecated construct to the alternative construct.
Answer5: There must be at least a one-year transition period between the release of the transitional version of Python and the release of the backwards incompatible version. Users will have at least a year to test their programs and migrate them from use of the deprecated construct to the alternative one.