Modules are pre-written packages of code that can be
used in a Python program.
They are similar to libraries in other languages.
Many standard modules exist, such as math (trig and other math functions), and string (useful string-handling functions).
You can also create new modules to encapsulate your own code.
A module is loaded using the import statement.
Once it's imported, all of a module's functions and variables are
accessible, through the module name.
>>> import math >>> math.sin(1) 0.8414709848078965