Proposal: local variable declarations and type advice

[Paul Rubin]

"Brian Quinlan" <brian at sweetapp.com> writes:

> Paul Rubin wrote: 
> 
> [snipped]
> > Python has grown from a tiny acorn to a healthy young tree.  I believe
> > any changes and additions to its design should be made with the idea
> > that it may become a mighty oak one day, i.e. that it will have
> serious
> > native-code optimizing compilers.   Language design changes should
> work
> > toward that goal, or at least not impede it.
> 
> Is optimization the only purpose of your proposals? If that is the case,
> they are probably not needed. The Python compiler already identifies
> variables that have local-only scope. Presumably other compilers could
> do the same.

Optimization is one of the goals of type advice.  Error checking is
another: in an appropriate runtime mode, it's similar to having an
assert statement every place the variable is set.

Local variable declarations are for code cleanliness.  Currently, using
some name for a temp variable leaves detritus around after you're done
with it.  To figure out what the program is doing, you have to check
whether further references to 'temp' really wanted the value left from
someplace far away, or were holding just a different temporary value.
When the usefulness of a variable ends, its scope should also end.