Chapter 6 – Collections | Python Zero to Hero

Objectives

Create and manipulate list objects: indexing, slicing, methods.
Define tuple for immutable sequences; unpacking.
Work with set: uniqueness, union, intersection, difference.
Manage dict: key–value access, methods, iteration.
Iterate through collections with for, enumerate, zip.
Build list and dict comprehensions for concise expressions.

1. Lists

Mutable, ordered sequences:

# Creation
fruits = ["apple", "banana", "cherry"]
empty = []

# Indexing & slicing
first = fruits[0]          # "apple"
subset = fruits[1:3]       # ["banana", "cherry"]

Common methods:

Method	Description	Example
`append(x)`	Add x at end	`fruits.append("date")`
`insert(i, x)`	Insert x at index i	`fruits.insert(1,"fig")`
`remove(x)`	Remove first x	`fruits.remove("banana")`
`pop([i])`	Remove & return item at i	`fruits.pop(2)`
`sort()`	Sort in place	`fruits.sort()`
`reverse()`	Reverse in place	`fruits.reverse()`
`extend(iter)`	Append items from iterable	`fruits.extend(["kiwi"])`

2. Tuples

Immutable, ordered sequences:

# Creation
coords = (10, 20)
single = (42,)        # trailing comma

# Unpacking
x, y = coords         # x=10, y=20

Tuples support indexing, slicing but not modification.

3. Sets

Unordered collections of unique elements:

# Creation
s = {1, 2, 3}
empty_set = set()

# Add/remove
s.add(4)
s.remove(2)

Set operations:

union: a | b
intersection: a & b
difference: a - b
symmetric_difference: a ^ b

4. Dictionaries

Key–value mappings:

# Creation
person = {"name": "Alice", "age": 30}
empty = {}

# Access & modify
name = person["name"]
person["city"] = "Rome"

Useful methods:

keys(), values(), items()
get(key, default), pop(key)
update(other_dict)

5. Iteration & Comprehensions

a) Iteration

for item in fruits:
    print(item)

for i, v in enumerate(fruits, 1):
    print(i, v)

for k, v in person.items():
    print(k, v)

b) List Comprehensions

# squares of even numbers 0–9
squares = [x*x for x in range(10) if x % 2 == 0]

# nested comprehension
pairs = [(i, j) for i in [1,2] for j in ['a','b']]

c) Dict Comprehensions

# map number to its square
sq_map = {x: x*x for x in range(5)}

Exercises

Create a list of numbers 1–20, slice out the even-indexed ones.
Use a tuple to store a sequence of coordinates and unpack them.
Given two sets, compute their union, intersection, and difference.
Build a dictionary from two lists: keys and values.
Write a list comprehension to filter and transform a list of strings.