Designing a module
A module is the unit of the Python implementation and reuse. All Python programming is provided at the module level. The class is the foundation of object-oriented design and programming. The module—a collection of classes—is a higher-level grouping and is the unit of reuse in Python. We can't easily reuse a single class in isolation. A properly designed module can be reused.
A Python module is a file. The filename extension must be .py. The filename in front of .py must be a valid Python name. Section 2.3 of Python Language Reference provides us with the complete definition of a name. One of the clauses in this definition is: Within the ASCII range (U+0001..U+007F), the valid characters for identifiers are the uppercase and lowercase letters A through Z, the underscore _ and, except for the first character, the digits 0 through 9.
OS filenames permit more characters from the ASCII range than Python names; this extra OS complexity must be ignored. The filename (without ...
