[Raymond Hettinger] > I propose that in Py3.0, the "and" and "or" operators be simplified to > always return a Boolean value instead of returning the last evaluated > argument.
> 1) The construct can be error-prone. When an error occurs it can be > invisible to the person who wrote it. I got bitten in published code > that had survived testing and code review: > def real(self): > 'Return a vector with the real part of each input element' > # do not convert integer inputs to floats > return self.map(lambda z: type(z)==types.ComplexType and z.real or z) The real problem, above, is the starve for using `lambda'. The abuse of `and' and `or' is a mere consequence of this. Remove `lambda' from Python, and most reasonable people would spontaneously write more legible code instead. I do not perceive Python as designed to prevent unreasonable people from "outclevering" themselves. > 2) When going back and forth between languages, it is easy to forget > that only Python returns something other than a boolean. C, C++, Lisp, and shells do the same as Python. Or maybe more correctly, Python borrowed short-circuiting booleans from other languages. > 3) Even when it isn't being used, the possibility of non-boolean > return value complicates the bytecode and parser. [...] P.S. > Simplifying "and" and "or" may create a need to introduce a > conditional operator but that is a discussion for another day. If removed, to be re-introduced differently, the bytecode and parser would not have gained simplicity overall. > Executive summary. Returning only Booleans reduces errors, makes > the code easier to review, follows other language norms, and > simplifies/speeds-up the generated code. The summary reduces to: "Returning only Booleans would speed-up the generated code, once in a while." Now, could we evaluate that speed up on the average code, like on the Python library say? It might not be worth the change... -- François Pinard http://pinard.progiciels-bpi.ca _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
