My (late) beef with Simple Generator syntax (PEP 255)

[Cameron Horn]

On Wednesday, Nov 13, 2002, at 02:26PM, <sismex01 at hebmex.com> wrote:

>> From: Cameron Horn [mailto:camhorn at mac.com]
>> Sent: Wednesday, November 13, 2002 4:26 PM
>>  
>> On Wednesday, Nov 13, 2002, at 02:19PM, <sismex01 at hebmex.com> wrote:
>> 
>> >> From: Cameron Horn [mailto:camhorn at mac.com]
>> >> Sent: Wednesday, November 13, 2002 4:20 PM
>> >>  
>> >> On Wednesday, Nov 13, 2002, at 02:16PM, David Eppstein 
>> >> <eppstein at ics.uci.edu> wrote:
>> >> 
>> >> >On 11/13/02 2:11 PM -0800 Cameron Horn <camhorn at mac.com> wrote:
>> >> >>> What I wonder is, why does it need to be a generator?  
>> >> What's wrong with
>> >> >>> def foo(): return ( )
>> >> >>> ?
>> >> >>
>> >> >> You're right if it's a one-time thing.  However, if I've got a
>> >> >> scaffolding like this, then it matters.
>> >> >>
>> >> >> def process_generator(function):
>> >> >>    for x in function():
>> >> >>       print x
>> >> >
>> >> >How does the function foo() I defined above fail to work in this 
>> >> >scaffolding?
>> >> 
>> >> In the "TypeError: iteration over non-sequence" sort of way.
>> >>
>> >
>> >An empty tuple is a sequence also;
>> >
>> >the "return ( )" thing is returning an empty tuple,
>> >not "None".  You can make it clearer by using
>> >"return tuple()" rather than "return ()".
>> 
>> Oops.  Missed those parentheses.  Then it is completely 
>> useful, unless you end up using the "next" method.
>>
>
>In that case, if you reckon you're going to use .next()
>directly, then you should change 'foo' to something like
>the following:
>
>def foo(): return iter(tuple())
>
>It's going to return a valid iterator which is going to
>try to iterate through an empty tuple, so it's going
>to raise StopIteration the first time you call .next().
>
>

Which is the obvious, clear and consistent way to create a generator that doesn't do anything.  Unless you're checking types or doing any other low-level things that you probably oughtn't.  I return to my original point.  And then, since everything works and I'm just complaining about a tiny bit of syntax, I shut up.