HyperText Transfer Protocol (HTTP):
HTTP is the basic protocol of the internet. With it, web pages are requested and sent. Python's httplib module exists for this purpose.
File Transfer Protocol (FTP):
Only slightly less known than HTTP is the File Transfer Protocol (FTP). This is the basic method of transferring files over the internet. Python speaks it with the ftplib module.
Post Office Protocol - Version 3 (POP3):
Most mail servers and clients currently use the third version of the Post Office Protocol (POP3). If you want to write a program that accesses a mailbox, you can use Python's pop module.
Internet Message Access Protocol (IMAP):
IMAP is an increasingly common way for email users to use one mailbox from multiple locations. With the imaplib module, Python programs can offer this functionality.
Simple Mail Transfer Protocol (SMTP):
People who use POP3 to receive their mail often use SMTP to send it. Python can send mail with the smtplib module.
Network News Transfer Protocol (NNTP):
If you like to read Usenet or the other newsgroups, you may recognize NNTP. It is the network standard for transferring newsgroup information. Python can interface with NNTP servers using the nntplib module.
Telnet :
Telnet is an older protocol which has largely fallen out of disuse these days. Some people still use it, however, and so Python speaks it using the telnetlib module.
Simple Object Access Protocol (SOAP):
SOAP is a very popular protocol currently. It is particularly useful for requesting and receiving small amounts of information at random intervals. Python speaks SOAP using the SOAPpy module.
Gopher:
Gopher is an older protocol that has not been widely used for many years. Nonetheless, some people still use it; therefore, Python speaks it using the gopherlib module.