"no variable or argument declarations are necessary."

[Paul Rubin]

Duncan Booth <duncan.booth at invalid.invalid> writes:
> If you think variable declarations should be required,

I don't think they should be required.  I think there should optional
declarations along with a compiler flag that checks for them if the
user asks for it, like Perl has.

> then you presumably want that to cover class attributes as well as
> local and global variables. After all assigning to 'x.i' when you
> meant 'x.j' is at least as bad as assigning to 'i'

Yes, lots of people mistakenly use __slots__ for exactly that purpose.
Maybe the function they think __slots__ is supposed to implement is a
legitimate one, and having a correct way to do it is a good idea.

> But unless you know the type of 'x', how do you know whether it
> has attributes 'i' or 'j'? 

If the compiler knows (through declarations, type inference, or
whatever) that x is a certain type of class instance, then it knows
what attributes x has.