I must admit I didn't. I felt confident it was restricted to adding and removing whitespace because the README says at the start: > Black ignores previous form

I must admit I didn't. I felt confident it was restricted to adding and removing whitespace because the README says at the start: > Black ignores previous formatting and applies uniform horizontal and vertical whitespace to your code. I now see it does sometimes modify non-whitespace characters e.g. later in the README it mentions: > In [certain] cases, parentheses are removed when the entire statement fits in one line I'm not in a position to test black out right now (I can't run Python on the computer I'm posting this comment on). I'd be curious to know what it does on the code I posted, and on over-length comments and string literals.