More Standard Modules
“Now, imagine that your friend kept complaining that she didn’t want to visit you since she found it too hard to climb up the drain pipe, and you kept telling her to use the friggin’ stairs like everyone else…”eff-bot, June 1998
This chapter describes a number of modules that are used in many Python programs. It’s perfectly possible to write large Python programs without using them, but they can help you save a lot of time and effort.
Files and streams
The fileinput module makes it easy to write different kinds of text filters. This module provides a wrapper class, which lets you use a simple for-in statement to loop over the contents of one or more text files.
UserDict, UserList, and UserString are thin wrappers on top of the corresponding built-in types. But unlike the built-in types, these wrappers can be subclassed. This can come in handy if you need a class that works almost like a built-in type, but has one or more extra methods.
Digests and encryption algorithms
The crypt module implements a DES-style one-way encryption. This module is usually only available on Unix systems.
The rotor module provides simple two-way encryption.