The Python Standard Library

One of the buzzwords used to describe Python is that it is a batteries included language, that is, it comes with a rich collection of built-in modules and packages called the Python Standard Library. If you've written any non-trivial Python program, you've almost certainly used modules from the Python Standard Library to do so. To get an idea of how vast the Python Standard Library is, here are a few example modules from this library:

Module	Description
datetime	Defines classes to store and perform calculations using date and time values
tempfile	Defines a range of functions to work with temporary files and directories
csv	Supports reading and writing of CSV format files
hashlib	Implements cryptographically secure hashes
logging	Allows you to write log messages and manage log files
threading	Supports multi-threaded programming
html	A collection of modules (that is, a package) used to parse and generate HTML documents
unittest	A framework for creating and running unit tests
urllib	A collection of modules to read data from URLs

These are just a few of the over 300 modules available in the Python Standard Library. As you can see, there is a vast range of functionality provided, and all of this is built in to every Python distribution.

Because of the huge range of functionality provided, the Python Standard Library is an excellent example of modular programming. For example, the math standard library module provides a range of mathematical functions that make it easier to work with integer and floating-point numbers. If you look through the documentation for this module (http://docs.python.org/3/library/math.html), you will find a large collection of functions and constants, all defined within the math module, that perform almost any mathematical operation you could imagine. In this example, the various functions and constants are all defined within a single module, making it easy to refer to them when you need to.

In contrast, the xmlrpc package allows you to make and respond to remote procedure calls that use the XML protocol to send and receive data. The xmlrpc package is made up of two modules: xmlrpc.server and xmlrpc.client, where the server module allows you to create an XML-RPC server, and the client module includes code to access and use an XML-RPC server. This is an example of where a hierarchy of modules is used to logically group related functionality together (in this case, within the xmlrpc package), while using sub-modules to separate out the particular parts of the package.

If you haven't already done so, it is worth spending some time to review the documentation for the Python Standard Library. This can be found at https://docs.python.org/3/library/. It is worth studying this documentation to see how Python has organized such a vast collection of features into modules and packages.

The Python Standard Library is not perfect, but it has been improved over time, and the library as it is today makes a great example of modular programming techniques applied to a comprehensive library, covering a wide range of features and functions.