backward/forward compatibility in PYTHON?

[Attila Horvath]

Dear PYTHON community,

I'm new to PYTHON but am considering it for a new project development. As
with any new language system I have a key concern:

	How is backward (and forward) compatibility resolved in PYTHON?

Scenario: I develop a system using version x.y and distribute it. My s/w
system finds its way to a client site using earlier version x.[y-1] of
PYTHON void of certain methods/features existing in my development
environment. I assume then that runtime errors will occur at the client
site. I also assume there are ways to determine if client's system is
compatible to run my distributed s/w.

Similar questions arise when bug fixes and/or certain functional
enhancements are made within PYTHON's builtin functions and methods from
version to version.

Is there a formal function & behavioral definition for PYTHON's each and
every builtin function and method to ensure consistency and forward
compatibility?

Attila