[Python-Dev] Community buildbots and Python release quality metrics

[Terry Reedy]

glyph at divmod.com wrote:

> to what extent should Python actually be compatible between releases?

As I understand things from years of observation, the following are fair 
game to changed in ways possibly backward-incompatible for specific 
code: bugs, detailed float behavior (which may be system-specific 
anyway), error messages, private interfaces, non-enforcement of 
documented rules, and defined implementation-dependent behavior.  But 
Guido has been somewhat conservative about this (least so for bug fixes, 
I think) and sometimes put off changes even when the fault lies with 
questionable usages.

One fly in the ointment is that bugs (a discrepancy between doc and 
code) may be fixed either by changing the doc or the code, according to 
which embodies the design intention.  So neither can be taken as gospel.