Is it possible to read FTP files without writing them using Python?

Well, you have the answer right in front of you: The FTP.retrbinary method accepts as second parameter a reference to a function that is called whenever file content is retrieved from the FTP connection.

Here is a simple example:

#!/usr/bin/env pythonfrom ftplib import FTPdef writeFunc(s):  print "Read: " + sftp = FTP('ftp.kernel.org') ftp.login()ftp.retrbinary('RETR /pub/README_ABOUT_BZ2_FILES', writeFunc)

You should implement writeFunc so that it actually appends the data read to an internal variable, something like this, which uses a callable object:

#!/usr/bin/env pythonfrom ftplib import FTPclass Reader:  def __init__(self):    self.data = ""  def __call__(self,s):     self.data += sftp = FTP('ftp.kernel.org') ftp.login()r = Reader()ftp.retrbinary('RETR /pub/README_ABOUT_BZ2_FILES', r)print r.data

Update: I realized that there is a module in the Python standard library that is meant for this kind of things, BytesIO:

#!/usr/bin/env pythonfrom ftplib import FTPfrom io import BytesIOftp = FTP('ftp.kernel.org') ftp.login()r = BytesIO()ftp.retrbinary('RETR /pub/README_ABOUT_BZ2_FILES', r.write)print r.getvalue()