On Sep 21, 2015, at 19:34, Stephen J. Turnbull firstname.lastname@example.org wrote:
Definitely, it should be mentioned in the PEP, but Python syntax is something that Python defines; shells and language variants have to be prepared to deal with Python syntax changes.
IIRC, back when the ternary conditional was suggested, and the C-style ?: was proposed, Guido declared that no way was his language ever going to use ? an operator. So if IPython took that as a promise that they can use ? without fear of ambiguity, you can't blame them too much....
I'm not saying they have a right to expect/demand that Guido never change his mind about anything anywhere ever, just that maybe they get a little extra consideration on backward compatibility with their use of ? than with their use of ! or % (which have been in use as operators or parts of operators for decades).