Fredrik Lundh writes ( about .append(x,y) ):
I suggest adding an explicit warning in the 1.6 docs, and removing it in the first post-1.6 release.
What about adding a command-line switch for enabling warnings, as has been suggested long ago? The .append() change could then print a warning in 1.6alphas (and betas?), but still run, and be turned into an error later.
That's better. I propose that the warnings are normally on, and that there are flags to turn them off or thrn them into errors. Alternatively, the default should be warnings == errors, with flags to turn them into warnings or turn them off. Turning them off by default seems to defeat the purpose -- only the most zealous will use them. The warning messages should show a source file and line number and display the source code line if available, just like in a traceback; but no traceback info should be printed. Also, a warning should only be printed once per message/file/lineno combination, per Python invocation. A dictionary could take care of this. Anybody care to further specify and then code up such a mechanism? --Guido van Rossum (home page: http://www.python.org/~guido/)