statements in control structures (Re: Conditional Expressions don't solve the problem)

[Anders J. Munch]

"Huaiyu Zhu" <huaiyu at gauss.almadan.ibm.com> wrote in message
news:slrn9sruhl.ll.huaiyu at gauss.almadan.ibm.com...
> I've been writing this for several evenings.  It's not polished, but IMHO
it
> solves most of the problems discussed in this thread.  So here it goes.
:-)
>
>
>                 PEP: Statements in Control Structures

Here's an additional alternative:

Use a function-like form let to perform assignment within expression.
  let(X,Y)
has the effect of doing
  X = Y
and returning the assigned object.

Example:

from sys import let
while let(x, get_next()):
  process(x)

Issues:
=======
* Syntax errors.
No new syntax to worry about.

* Obuscation.
- Python function do not usually modify caller variables.
+ A reader of this code who doesn't know let can find out about it using
through the usual mechanism,  sys.let.__doc__.

* Compatibility.
No compatibility issues; let is not a keyword.

* Generality.
Doesn't allow arbitrary statements to be executed.
Does allow short circuit conditions.

* Implementation.
Hackish.  Introducing a let keyword would be cleaner.

- Anders