Why is it possible to replace sometimes set() with {}?

Question

In PyCharm, when I write:

return set([(sy + ady, sx + adx)])

it says \"Function call can be replaced with set literal\" so it repl

Answer 1

Another example how set and {} are not interchangeable (as jonrsharpe mentioned):

In: f = 'FH'

In: set(f)
Out: {'F', 'H'}

In: {f}
Out: {'FH'}