This sounds similar to Dropbox's PyAnnotate -- Guido van Rossum writes about it here: http://mypy-lang.blogspot.co.uk/2017/11/dropbox-releases-pya...
Would be interesting to see how MonkeyType and PyAnnotate compare.
Would be interesting to see how MonkeyType and PyAnnotate compare.
PyAnnotate couples re-applying the types with the tool, and uses type comments for this.
MonkeyType generates .pyi files that you can either use directly or re-apply them to your code as proper type annotations.
Other than that, MonkeyType is used on a daily basis internally and solves a bunch of common annoyances of systems like these, like duplicates in unions, applying better types to stuff that was already hand-annotated with Any, etc.
I'd also like to know how much quicker or better it could have been completed if it had been done out in the open.
We knew we're going to open-source each others' implementations, esp. that Instagram's is focusing solely on Python 3 which isn't useful for Dropbox at the moment. It just took a while to get through the process of open sourcing what we had (cleaning up the early implementation with limited documentation, decoupling from internal data stores, etc.).
Would it be cheaper if this started out in the open? Probably, but I don't think by quite the margin as you expect.
I assume they scratched their own itch so it was probably faster to do it on their own addressing their specific needs.