On 8 September 2016 at 04:18, Guido van Rossum
There's been some quite contentious discussion about the PEP, on and off python-dev, regarding how the mere presence of annotation syntax in the language will change the way people will see the language. My own experience using mypy and PyCharm has been quite different: annotations are a valuable addition for large code bases, and it's worth the effort to add them to large legacy code bases (think millions of lines of Python 2.7 code that needs to move to Python 3 by 2020). The effect of this has been that engineers using Python are happier and more confident that their code works than before, have an easier time spelunking code they don't know, and are less afraid of big refactorings (where conversion to Python 3 can be seen as the ultimate refactoring).
I also don't think it hurts to make the language migration easier for folks coming from a C/C++/C#/Java background, and even if they initially use explicit hints more heavily than they need to given the inferencing engines in typecheckers, those same hints have the potential to enable more automated refactorings that simplify their code. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia