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

[Martin Franklin]

Martin Franklin wrote:
> Robert wrote:
> 
>> I just tried to convert a (hugh size) ftp.retrbinary run into a
>> pseudo-file object with .read(bytes) method in order to not consume
>> 500MB on a copy operation.

[snip]

> 
> 
> Hmmmm this is nearly there I think...:

whoops... spoke too soon..

> 
> import ftplib
> 
> class TransferAbort(Exception): pass
> 
> class FTPFile:
>     def __init__(self, server, filename):
>         self.server = server
>         self.filename = filename
>         self.offset = 0
> 
>     def callback(self, data):
>         self.offset = self.offset + len(data)
>         self.data = data
>         ## now quit the RETR command?
>         raise TransferAbort("stop right now")
> 
>     def read(self, amount):
>         self.ftp = ftplib.FTP(self.server)
>         self.ftp.login()


I needed to insert a time.sleep(0.1) here as the connections were
falling over themselves - I guess testing with a blocksize of 24
is a little silly.


>         try:
>             self.ftp.retrbinary("RETR %s" %self.filename, self.callback,
>                 blocksize=amount,
>                 rest=self.offset)
>         except TransferAbort:
>             return self.data
> 
> 
> f = FTPFile("HOSTNAME", "FILENAME")
> 
> print f.read(24)
> print f.read(24)
> 

## new test...

f = FTPFile("HOSTNAME", "FILENAME")

while 1:
     data = f.read(24)
     if not data:
         break
     print data,


> 
> I open the ftp connection inside the read method as it caused an error 
> (on the second call to read) when I opened it in  __init__ ???
> 
> HTH
> Martin
> 
>