There's been discussion here and on python-dev regarding PEP 526 that assumes there will be multiple type checkers for Python. I really can't see this happening. If typing annotations become common or maybe considered best practice, the Zen of Python "there should be one-- and preferably only one --obvious way to do it" will take effect. Firstly, the interpreter will need to have type checking built in. Just about every intro book and tutorial for Python says how great it is that you don't have an edit-save-compile cycle, just fire up the Python interpreter and start typing. Having to run a separate type checker will be considered as ridiculous as a C compiler that didn't run the preprocessor itself. Secondly, PyPI will collapse if there isn't just one. How can we express dependencies between packages that use different type checkers? When type checkers themselves have versions? When a dev team uses one type checker for 1.x and then switches to another for 2.x? That's a special circle of hell. -- cheers, Hugh Fisher