convert ftp.retrbinary to file object? - Python language lacks expression?

[Steve Holden]

Robert wrote:

> That turns into periodic new RETR commands with offset. Think its more 
> an "odd" trick. I'd even prefer a threaded approach (thread puts the 
> blocks into a stack; a while ... yield generator loop in the main thread 
> serves the .read() function of the pseudo file object, which is my 
> wish). Yet such tricks are all kind of OS-level tricks with a lot of 
> overhead.
> 
> I wonder really, if the Python language itself can express an elegant 
> flat solution to turn the block delivering callback function into a 
> generator/.read(bytes) solution? I found no way.
> 
Don't know whether this would be helpful as a starting point, but a 
while (hmm, some years ...) ago I wrote an example of how FTP could be 
used as a file-like object. Look for ftpStream.py on

   http://www.holdenweb.com/Python/

Of course, in those days files could do a bit less than they can now, so 
there's no attempt to provide an iterator interface.

> (Looking over some Ruby stuff, Ruby seems to be able to do so from the 
> language. I am not really familiar to Ruby. I always felt Python to be 
> as complete - but much more clean. I became somewhat jealous ... :-) )
> 
> As the solution in my case has to stand many different file systems 
> compatibly ( file.read(bytes) function !) and also other FTPS & SFTP 
> classes with different retrbinary functions have to be compatible, I 
> cannot even make a simple FTP subclassed retrbinary without getting 
> really weired. Thus the existing .retrbinary with callback is the 
> "official interface in this game".
> 
You will note that my code uses delegation to an FTP object rather than 
inheritance. Maybe you would find that approach more fruitful for your 
application.

regards
  Steve
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Steve Holden                           http://www.holdenweb.com/