Bioinformatics Programming Using Python

Appendix B. Collection Type Summary

This appendix provides a compact summary of (most of) Python’s collection types. It describes the characteristics and methods of each collection and the operators and functions used with collection values. At the end of the appendix, you will find summaries of the collection iteration templates shown in Chapter 4.

Types and General Operations

Table B-1 summarizes the characteristics of Python’s most commonly used collection types. The column labeled “Syntax” shows examples of two-element collections, with e1 and e2 representing elements of any type and k1 and k2 representing instances of an immutable type.

Table B-1. Collection types

Element access	Name	Type	Element type	Mutable?	Syntax
Unordered unique elements	Set	set	Any immutable	Yes	{k1, k2}
	Frozenset	frozenset	Any immutable	No	None
Ordered (indexed)	String	str	One-character strings[a]	No	'ac' "ac" '''ac''' """ac"""
	Bytes	bytes	8-bit bytes[b]	No	b'ac' b"ac" b'''ac''' b"""ac"""
	Bytearray	bytearray	8-bit bytes	Yes	None
	Range	range	Integers	No	None
	Tuple	tuple	Any	No	(e1, e2)
	List	list	Any	Yes	[e1, e2]
Associative	Dictionary	dict	Keys immutable, values any	Yes	{k1:e1, k2:e2}
Stream (next)	File object	Depends[c]	Characters, bytes, lines	Depends on use	None
[a] Strings don’t really “contain” characters or one-character strings, but for many purposes they behave as if they do. [b] Bytes are equivalent to the integers from 0 through 255. [c] The type of the object returned by open is an instance of the class from the IO library; it isn’t one of the built-in collection ...