Python 3 isinstance

[MRAB]

Lambert, David W (S&T) wrote:
> Overly terse.  I do mean that this is illegal:
> 
> isinstance(s, {str, bytes})
> 
> tuples have order, immutability, and the possibility of repeat items.
> 
> A set is most reasonable in a mathematical sense.
> 
You could say the same about s.startswith(("a", "b")).

It might be because sets are a more recent addition to the language; if 
they had been in Python from the start then maybe they would've been 
used instead.