Python Programming On Win32

Fetching Data via FTP

The ftplib module is used in much the same way as the httplib module: a single class, FTP, provides all of the functionality.

The FTP protocol supports a variety of commands, which include such operations as logging in, navigating the filesystem, and retrieving directory listings. Let’s create an FTP session:

>>> import ftplib
>>> ftp = ftplib.FTP('ftp.python.org') # connect to host, default port
>>>

Log on as an anonymous user:

>>> ftp.login('anonymous', '[e-mail]')
"230-WELCOME to python.org, the Python programming language ..."
>>>

Get a directory listing:

>>> ftp.retrlines('LIST') # list directory contents
total 38
drwxrwxr-x  11 root     4127         512 Aug 28 20:23 .
...
-r--r--r--   1 klm      1000         764 Aug 25 19:32 welcome.msg
'226 Transfer complete.'

Notice there’s a file welcome.msg: let’s download the file. Open a local file and indicate its write method should be called to store the data:

>>> file=open("welcome.msg", "w")
>>> ftp.retrlines("retr welcome.msg", file.write)
'226 Transfer complete.'
>>> file.close()

Now reopen the file and print the data:

>>> open("welcome.msg", "r").read()
"WELCOME to python.org, the Python programming language home site. ..."
>>>

To retrieve a binary file (such as an executable), you could use the method retrbinary() ; it takes the same methods as retrlines() , except it also allows you to specify a block size for the transfer. In this case you should remember to open the file itself in binary mode, as discussed in Chapter 3.