PEP 289: Generator Expressions (please comment)

[Alex Martelli]

Daniel Dittmar wrote:

> Raymond Hettinger wrote:
>>     bestplayer, bestscore = max( (p.score, p.name) for p in players )
>> 
>> Each of the above runs without creating a full list in memory,
>> which saves allocation time, conserves resources, and exploits
>> cache locality.
> 
> Why should generator comprehension be useful only for arguments?

Nobody ever said it would be.  RH's examples were all function
calls because that's an "obvious" use case.


> counter proposal:
> g[(p.score, p.name) for p in players ]

Looks like it's indexing g.

> This works similar to r'\' for raw strings and u'x' for unicode strings.

Nope, it's ambiguous, while <single letter> adjacent to '...' isn't.

> This has the advantage that it can be more easily extended:
> d[(p.name, p.score) for p in players] creates a dictionary

dict((p.name, p.score) for p in players)

will do it in a much more obvious way.

> s[(p.score, p.name) for p in players] creates a sorted list

list.sorted((p.score, p.name) for p in players)

will do it in a much more obvious way, and also allow you to
specify such optional niceties as (e.g.) "key=" (in 2.4 --
and, btw, thanks to all of RH's work on the issue!).

> and
> p[$*-=%/sd/!] allows to embed perl code

If you want perl, you know where to find it.


Alex