[Python-Dev] RFC: generator combinator syntax
Steven D. Majewski
Fri, 3 Aug 2001 19:35:04 -0400 (EDT)
On Fri, 3 Aug 2001, Paul Prescod wrote:
> I propose:
> [yield file for file in Files('.')
> if file.lower.find(.'gif')>=0]
> By reusing the yield keyword we can get rid of the need for the new "|"
> or "&" syntax.
> Any kind of combination that can be done with list comprehensions would
> be possible with generator comprehensions.
I assume you intend that "[yield file for..." expression to evaluate
to a generator, not a list.
I like it.
I'm not sure that I want to get rid of the operator syntax.
I'm still getting used to it.
Either works a lot better than using filter: I was complaining
in an earlier thread about having to explicitly ask for the
.next attrib. It just took a while to figure out how they are
meant to be used.
Generators & Iterators really seem to open up functional programming
I'm trying to put together some more basic file processing functionals:
for example, fileExt(ext) instead of isGif:
return lambda s: os.path.splitext( s )[-1].lower() == ext.lower()
Then isGif becomes:
isGif = fileExt( '.gif' )
and others like fileSize, owner, etc.
def fileSize( test ):
return lambda s: test( os.stat(s)[stat.ST_SIZE] )
and folding the Genops class into the File function, I can
do things like:
for file in Files() & isGif & fileSize( lambda s : s > 1024 ):
process( file )