[timhh]

I did a blind survey of YAPF vs Black at my work. The results came back as 70% in favour of Black.

Black gives generally nicer output, and also more predictable output because its folding algorithm is simpler. YAPF uses a global optimisation which makes it make very strange decisions sometimes. Black does too, but much less often.

There are also non-style problems with YAPF. It occasionally fails to produce stable output, i.e. yapf(yapf(x)) != yapf(x). In some cases it never stabilises - flip flopping between alternatives forever!

Finally it seems to have very bad worst case performance. On some long files it takes so long that we have to exclude them from formatting. Black has no issue.

In conclusion, don't use YAPF! Black is better in almost every way!

[VectorLock]

How did you perform the blind survey? Format some code with Black and YAPF and ask people which they liked better?

[timhh]

Yeah exactly. I had 20 samples from our codebase that showed some representative differences and you had to click on which one you liked more. The order (Black/YAPF or YAPF/Black) was randomised.

I also had to turn off Black's quote normalisation otherwise it is really obvious which is which. Quote normalisation is another point in Black's favour.

I could put the survey up somewhere if anyone is interested.