[Python-Dev] PEP 340: Only for try/finally?

[Phillip J. Eby]

At 11:54 PM 5/3/05 +0200, BJörn Lindqvist wrote:
>It seems like the possibilities are endless. Maybe too endless?
>Because this new feature is so similar to anonymous functions, but is
>not quite anonymous functions, so why not introduce anonymous
>functions instead, that could make all the things block can, and more?
>But as I said, I'm misunderstanding something.

Anonymous functions can't rebind variables in their enclosing function.  It 
could be argued that it's better to fix this, rather than inventing a new 
macro-like facility, but I don't know how such a rebinding facility could 
preserve readability as well as PEP 340 does.

Also, many of your examples are indeed improvements over calling a function 
that takes a function.  The block syntax provides a guarantee that the 
block will be executed immediately or not at all.  Once you are past the 
block suite in the code, you know it will not be re-executed, because no 
reference to it is ever held by the called function.  You do not have this 
same guarantee when you see a function-taking-function being invoked.  So, 
a block suite tells you that the control flow is more-or-less linear, 
whereas a function definition raises the question of *when* that function 
will be executed, and whether you have exhaustive knowledge of the possible 
places from which it may be called.