We have a 50kloc all-python backend, with very high (>90%) type integration (that last mile is hard). I've done pretty big (thousands of loc) refactors and it's

We have a 50kloc all-python backend, with very high (>90%) type integration (that last mile is hard). I've done pretty big (thousands of loc) refactors and it's pretty painless. Night and day compared to the pre-typed python days.