Sequences

6. Sequences#

This chapter presents Python’s sequence types for storing values in order: lists and tuples. You will compare mutable and immutable sequences, and see how aliasing and copying affect programs that share lists, so you can choose the right structure for a task.

Creating and using lists and tuples
Accessing sequences with indexes and slices
Adding, removing, and transforming lists
Comparing mutability, identity, aliasing, and copying
Applying common sequence idioms used in everyday Python

Chapter Video

This overview introduces Python’s sequence containers, lists and tuples. Its last part covers sets, which Chapter 7 presents in detail.

Python Tutorial for Beginners 4: Lists, Tuples, and Sets (29:04) by Corey Schafer

Hosted on YouTube; property of its original creator, embedded here for educational reference only.

Learning Objectives

By the end of this chapter, you will be able to:

Construct and manipulate Python lists using indexing, slicing, and core list methods
Explain object identity, aliasing, shallow copies, and deep copies
Predict how lists behave when passed to functions
Use list comprehensions, unpacking, enumerate(), zip(), and sorting patterns
Use tuples for fixed records, including tuple unpacking, returning multiple values from a function, packing arguments with *args, and named tuples

Chapter Flow

Glossary

#	Term	Explanation
1	Collection	An object that stores multiple values.
2	Sequence	An ordered collection whose items can be accessed by position.
3	List	An ordered, mutable sequence of values.
4	Tuple	An ordered, immutable sequence of values.
5	Mutability	Whether an object can be changed after it is created.
6	Immutable	Describes an object whose contents cannot be changed after creation.
7	Index	An integer position used to access an item in a sequence.
8	Slice	A selected range of items from a sequence.
9	List comprehension	A compact expression for building a list from an iterable.
10	Nested list	A list that contains other lists as elements.
11	Aliasing	Two or more names referring to the same object.
12	Shallow copy	A copy of a collection that still shares nested objects with the original.
13	Deep copy	A copy that recursively copies nested objects.
14	Unpacking	Assigning items from a collection to separate names.
15	`enumerate`	A built-in function that produces index-value pairs during iteration.
16	`zip`	A built-in function that pairs items from multiple iterables.
17	Identity	The property that distinguishes one object from another; `is` checks whether two names refer to the same object.
18	Reference	The association between a variable and the object it refers to.
19	Named tuple	A tuple whose fields can also be accessed by name, created with `namedtuple` from the `collections` module.
20	Key function	A function passed as the `key` argument to `sorted`, `min`, or `max` that computes the value used to compare each item.
21	Record	A group of related values that describe one thing, such as one sale or one student, often stored as a tuple.
22	Argument packing (`*args`)	Collecting any number of extra positional arguments into a tuple through a parameter whose name begins with `*`.
23	Equivalent	Describes two objects that have the same value, which `==` checks.
24	Identical	Describes two names that refer to the same object, which `is` checks.
25	Lexicographic comparison	Comparing two sequences element by element from the start, so the first pair of items that differ decides the result.