> That's why I ran the micro-benchmark and, in fact, I was expecting %-interpolation to be faster exactly because it is less flexible.

Actually %-interpolation is more flexible.

>>> '%x' % 123
'7b'
>>> '%0X' % 123
'7B'
>>> '%#x' % 123
'0x7b'
>>> '%04x' % 123
'007b'

If document alternatives for hex(), we should also document formatting alternatives for bin(), oct(), repr(), ascii(), str(), chr(), str.ljust(), str.rjust(), str.center(), str.zfill().