Iyad Ahmed writes:
> Example use cases:
>
> - Loop variables and similar, it is sometimes more comfortable to scope
> it to the loop body only
> - Not having to name variables var1, var2, var3, or makeup unnecessarily
> unique variable names, in some situations
I am not authoritative, so don't take this as a denial of the idea,
but I want to give you some idea of why I suspect it is unlikely to
succeed.
1. Python has a well-defined notion of *suites*, ie, indented groups
of statements. If this were going to happen, I would imagine that
it would be at the statement level, and most likely the syntax
would be something like "block:" or "scope:" followed by an
indented suite. (This is a quibble about syntax, not a reason it
would be opposed in principle.)
2. Many statements in Python have suites, but only class and def
create scopes. This is by design. It makes the rules for scopes
simple. Since they can be used anywhere a statement can go, you
can use them to create scopes (at the cost of having to invoke
them later, of course). The exceptional case is that
comprehensions have been changed to not leak their iteration
variables, but this is basically done by implicitly defining and
calling a function to create the scope if I remember correctly.
3. It's often useful to refer to the loop variable after exiting a
loop. For example, if there's an explicit break in a loop
controlled by a range or list, the loop variable tells you how far
you got before exiting. I doubt a proposal to "close" the scope
of the loop variable would be accepted.
4. It's generally considered bad style to have very long or deeply
indented function bodies. Variable name collisions are more
likely with global variables than with other variables in the same
local scope. Perhaps for this reason, Python programmers don't
frequently request more scopes. Again, the exception was the
change in comprehension semantics mentioned above. which was a
pain point for many. Programmers tend to think of displays more
as "variable literals" than as "open-coded constructors", and
therefore expect the scope to be closed.
Again, I'm not authoritative, but my recommendation is to consider the
above points carefully while advocating this idea.
Steve
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