Fluent Python

Chapter 2. An Array of Sequences

As you may have noticed, several of the operations mentioned work equally for texts, lists and tables. Texts, lists and tables together are called trains. […] The FOR command also works generically on trains.¹

Geurts, Meertens, and Pemberton, ABC Programmer’s Handbook

Before creating Python, Guido was a contributor to the ABC language—a 10-year research project to design a programming environment for beginners. ABC introduced many ideas we now consider “Pythonic”: generic operations on sequences, built-in tuple and mapping types, structure by indentation, strong typing without variable declarations, and more. It’s no accident that Python is so user-friendly.

Python inherited from ABC the uniform handling of sequences. Strings, lists, byte sequences, arrays, XML elements, and database results share a rich set of common operations including iteration, slicing, sorting, and concatenation.

Understanding the variety of sequences available in Python saves us from reinventing the wheel, and their common interface inspires us to create APIs that properly support and leverage existing and future sequence types.

Most of the discussion in this chapter applies to sequences in general, from the familiar list to the str and bytes types that are new in Python 3. Specific topics on lists, tuples, arrays, and queues are also covered here, but the focus on Unicode strings and byte sequences is deferred to Chapter 4. Also, the idea here is to cover sequence types ...