PEP 315: Enhanced While Loop

[Andrew Koenig]

>> On the other hand, I proposed essentially the same idea for C back in
>> 1977.  Unfortunately, Dennis didn't think it was worth the effort :-)

Oren> But C does allow assignment inside expressions, three-way conditionals
Oren> and comma as "evaluate both, return right". Together they cover most of 
Oren> what people might want the "setup" part for.

Yes.

Oren> But adding such features to Python expressions will be quite unpythonic.

Let's not talk about PEP308, OK?

>> while:
>> <setup code>
>> and while <condition>:
>> <loop body>

Oren> Nice. No new keywords. Cannot be easily confused with a C do/while loop.
Oren> This probably improves BDFL acceptance factor from -10 to -7 or better!

That's my guess too.

I must confess that I find this issue less important now that we have
generators.  Before that, I was looking for a clean way of writing

	     while True:
	         line = infile.read()
		 if not line:
		     break
		 <process a line>

but with generators it is possible to write

	 for line in infile:
	     <process a line>

(Yes, I know that you don't need generators to allow such usages for
built-in types, but generators make it much easier to do similar things
with user-defined types)