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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: Documentation, assignment in expression.
Date: Fri, 23 Mar 2012 21:09:16 -0400
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On Fri, 23 Mar 2012 23:59:44 +0100, Alexander Blinne <news@blinne.net>
declaimed the following in gmane.comp.python.general:

> Hi,
> 
> I think this section of the docs needs some kind of rewrite:
> 
> <http://docs.python.org/faq/design.html#why-can-t-i-use-an-assignment-in-an-expression>
> 
> While it is great to discuss the reasons for not allowing an assignment
> in an expression, I feel that the given example is some kind of
> outdated. The last sentence "For example, in the current version of
> Python file objects support the iterator protocol, so you can now write
> simply (for line in file:)" makes me think that this section was written
> while that syntax was still new. No one I know would ever write
> something like this:
> 
> > while True:
> >     line = f.readline()
> >     if not line:
> >         break
> >     ... # do something with line
> 
> I think at least we need a new example. Any ideas?
>
	But remember -- this is a section on why no "assignment in
expression"...

	That means 

for line in f:
	#do stuff

is the counter to the equivalent C-style

while (line = f.readline() ):	#mixing C style with Python calls
	# do stuff

	The section is not meant to be an advocate for or against your true
Python design using an infinite loop, and separate input line.

	The emphasis on "current version" might do with updating -- by
explicitly stating when the iteration came in...
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
        wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/