python list tuples dictionaries and set a bit more details

@amitmund June 20, 2026

Python Collections Master Guide

Lists, Tuples, Dictionaries, and Sets

This guide covers:

  • Concepts
  • Syntax
  • Real-world examples
  • Important methods
  • Common mistakes
  • Common errors
  • Comparisons
  • Time complexity basics
  • Interview questions
  • Practice exercises
  • Homework

Table of Contents

  1. Introduction
  2. List
  3. Tuple
  4. Dictionary
  5. Set
  6. Collection Methods Cheat Sheet
  7. Comparison Table
  8. Common Beginner Mistakes
  9. Real-World Combined Example
  10. Time Complexity Basics
  11. Interview Questions
  12. Homework

1. Introduction

Python provides four major collection types:

Collection Ordered Mutable Duplicates Access
List ✅ ✅ ✅ Index
Tuple ✅ ❌ ✅ Index
Dictionary ✅ (3.7+) ✅ Keys ❌ Values ✅ Key
Set ❌ ✅ ❌ Membership

Quick Memory Trick

LIST  -> Changeable Collection
TUPLE -> Fixed Collection
DICT  -> Key-Value Collection
SET   -> Unique Collection

2. LIST

What is a List?

A List is an ordered collection that can be modified after creation.

Syntax

fruits = ["Apple", "Banana", "Orange"]

Real-World Example

shopping = ["Milk", "Bread", "Eggs"]

print(shopping)

Output:

['Milk', 'Bread', 'Eggs']

Accessing Elements

shopping = ["Milk", "Bread", "Eggs"]

print(shopping[0])
print(shopping[-1])

Output:

Milk
Eggs

Updating Elements

shopping[1] = "Brown Bread"

Most Important List Methods

append()

Adds item at end.

numbers = [1, 2, 3]

numbers.append(4)

print(numbers)

Output:

[1, 2, 3, 4]

extend()

Adds multiple elements.

numbers = [1, 2]

numbers.extend([3, 4, 5])

print(numbers)

Output:

[1, 2, 3, 4, 5]

insert()

numbers = [1, 2, 3]

numbers.insert(1, 100)

print(numbers)

Output:

[1, 100, 2, 3]

remove()

Removes first occurrence.

numbers = [1, 2, 3]

numbers.remove(2)

print(numbers)

Output:

[1, 3]

pop()

Removes and returns element.

numbers = [1, 2, 3]

x = numbers.pop()

print(x)
print(numbers)

Output:

3
[1, 2]

clear()

numbers = [1, 2, 3]

numbers.clear()

print(numbers)

Output:

[]

index()

fruits = ["Apple", "Banana", "Orange"]

print(fruits.index("Banana"))

Output:

1

count()

numbers = [1, 2, 2, 2, 3]

print(numbers.count(2))

Output:

3

sort()

numbers = [5, 1, 4, 2]

numbers.sort()

print(numbers)

Output:

[1, 2, 4, 5]

reverse()

numbers.reverse()

copy()

a = [1, 2, 3]

b = a.copy()

print(b)

Useful Built-in Functions

numbers = [10, 20, 30]

print(len(numbers))
print(max(numbers))
print(min(numbers))
print(sum(numbers))

Common Errors

IndexError

data = [1, 2]

print(data[10])

Output:

IndexError: list index out of range

ValueError

data = [1, 2]

data.remove(5)

Output:

ValueError

3. TUPLE

What is a Tuple?

A Tuple is an ordered but immutable collection.

Syntax

data = (1, 2, 3)

Real-World Example

coordinate = (20.2961, 85.8245)

print(coordinate)

Tuple Methods

Tuple has very few methods because it cannot be modified.

count()

numbers = (1, 2, 2, 3)

print(numbers.count(2))

Output:

2

index()

numbers = (10, 20, 30)

print(numbers.index(20))

Output:

1

Tuple Unpacking

name, age = ("Rahul", 20)

print(name)
print(age)

Returning Multiple Values

def get_user():
    return ("Rahul", 20)

name, age = get_user()

Common Errors

TypeError

data = (1, 2, 3)

data[0] = 100

Output:

TypeError

ValueError

name, age, city = ("Rahul", 20)

Output:

ValueError

Beginner Mistake

x = (5)

Output:

<class 'int'>

Correct:

x = (5,)

4. DICTIONARY

What is a Dictionary?

Stores data using key-value pairs.

Syntax

student = {
    "name": "Rahul",
    "age": 20
}

Real-World Example

employee = {
    "id": 101,
    "name": "John",
    "salary": 50000
}

Accessing Values

print(employee["name"])

Most Important Dictionary Methods

get()

Safe access.

print(employee.get("salary"))

keys()

print(employee.keys())

values()

print(employee.values())

items()

print(employee.items())

update()

employee.update({"city": "Bhubaneswar"})

pop()

employee.pop("salary")

popitem()

Removes last item.

employee.popitem()

clear()

employee.clear()

copy()

new_employee = employee.copy()

setdefault()

employee.setdefault("country", "India")

Adds key only if absent.

Nested Dictionary

employee = {
    "name": "John",
    "address": {
        "city": "Bhubaneswar",
        "state": "Odisha"
    }
}

print(employee["address"]["city"])

Iterating

for key, value in employee.items():
    print(key, value)

Common Errors

KeyError

student = {"name": "Rahul"}

print(student["age"])

Output:

KeyError

Safe:

student.get("age")

Unhashable Type

data = {
    [1, 2]: "test"
}

Output:

TypeError: unhashable type: 'list'

5. SET

What is a Set?

A Set stores unique values only.

Syntax

skills = {"Python", "SQL"}

Removing Duplicates

numbers = [1,1,2,2,3,3]

unique = set(numbers)

print(unique)

Output:

{1,2,3}

Most Important Set Methods

add()

skills.add("Java")

Example

skills = set()

# print(type(skills))

print(skills) # its with word set, because with just (), you might consider its as tuple.

skills.add("Java")

print(skills)

update()

skills.update(["C++", "Go"])

remove()

skills.remove("Java")

Raises error if absent.

discard()

skills.discard("Java")

Safe version.

pop()

Removes random element.

skills.pop()

clear()

skills.clear()

copy()

new_skills = skills.copy()

Set Operations

A = {1,2,3,4}
B = {3,4,5,6}

Union

A.union(B)
# or
A | B

Intersection

A.intersection(B)
# or
A & B

Difference

A.difference(B)
# or
A - B

Symmetric Difference

A.symmetric_difference(B)
# or
A ^ B

issubset()

{1,2}.issubset({1,2,3})

Output:

True

issuperset()

{1,2,3}.issuperset({1,2})

Output:

True

Common Errors

KeyError

skills.remove("Rust")

Output:

KeyError

Use:

skills.discard("Rust")

Unhashable Type

data = {[1,2], [3,4]}

Output:

TypeError

6. Collection Methods Cheat Sheet

List

append()
extend()
insert()
remove()
pop()
clear()
index()
count()
sort()
reverse()
copy()

Tuple

count()
index()

Dictionary

get()
keys()
values()
items()
update()
pop()
popitem()
clear()
copy()
setdefault()

Set

add()
update()
remove()
discard()
pop()
clear()
copy()
union()
intersection()
difference()
symmetric_difference()
issubset()
issuperset()

7. Comparison Table

Feature List Tuple Dictionary Set
Ordered ✅ ✅ ✅ ❌
Mutable ✅ ❌ ✅ ✅
Duplicates ✅ ✅ Keys ❌ ❌
Indexing ✅ ✅ ❌ ❌
Key Lookup ❌ ❌ ✅ ❌
Unique Values ❌ ❌ Keys Only ✅

8. Common Beginner Mistakes

Mistake 1

student = {}

Creates Dictionary, not Set.

Correct:

student = set()

Mistake 2

x = (5)

Creates integer.

Correct:

x = (5,)

Mistake 3

for i in range(len(numbers)+1):
    print(numbers[i])

Produces:

IndexError

Mistake 4

a = [[0] * 3] * 3

Unexpected behavior due to shared references.

Better:

a = [[0 for _ in range(3)] for _ in range(3)]

9. Real-World Combined Example

student = {
    "name": "Amit",
    "marks": [85, 90, 88],
    "location": (20.2961, 85.8245),
    "skills": {"Python", "SQL"}
}

print(student["name"])
print(student["marks"])
print(student["location"])
print(student["skills"])

Uses: - Dictionary - List - Tuple - Set

Together in a single object.

10. Time Complexity Basics

Operation List Tuple Dictionary Set
Access O(1) O(1) O(1) N/A
Search O(n) O(n) O(1) Avg O(1) Avg
Insert End O(1) N/A O(1) O(1)
Delete O(n) N/A O(1) O(1)

11. Interview Questions

Basic

  1. Difference between List and Tuple?
  2. Difference between Set and List?
  3. Difference between Dictionary and List?
  4. Why are Set values unique?
  5. Why are Dictionary keys unique?

Intermediate

  1. What is tuple unpacking?
  2. What is a nested dictionary?
  3. Difference between remove() and pop()?
  4. Difference between remove() and discard()?
  5. Why is Tuple immutable?

Advanced

  1. Why must Dictionary keys be immutable?
  2. How does a Set remove duplicates?
  3. Average complexity of Dictionary lookup?
  4. Difference between shallow copy and deep copy?
  5. When should you use a Set instead of a List?

12. Homework

Beginner

Q1

Create a list of 5 favorite movies.

Tasks: - Print - Add movie - Remove movie - Sort movies

Q2

Create a tuple containing:

(day, month, year)

Print values separately.

Q3

Create a Book Dictionary:

{
    "title": "...",
    "author": "...",
    "price": ...
}

Tasks: - Update price - Add publisher - Delete publisher

Q4

Convert:

["apple", "banana", "apple", "orange"]

into a Set.

Explain why duplicates disappeared.

Intermediate

Q5

Given:

marks = [78,88,95,67,84]

Find: - Sum - Average - Highest - Lowest

Q6

Employee Dictionary:

employee = {
    "name": "John",
    "salary": 50000
}

Increase salary by 10%.

Q7

Perform:

A = {1,2,3,4}
B = {3,4,5,6}

Find: - Union - Intersection - Difference - Symmetric Difference

Advanced

Q8

Student Database:

students = [
    {"name": "Rahul", "marks": 80},
    {"name": "Amit", "marks": 92},
    {"name": "Priya", "marks": 88}
]

Find: - Topper - Average marks

Q9

Remove duplicates from:

[1,2,3,2,5,1,6,3]

Without using set().

Q10

Create Contact Book

Features: - Add Contact - Delete Contact - Update Contact - Search Contact

Q11

Create Word Frequency Counter using Dictionary.

Q12

Create Inventory System using Dictionary.

Q13

Find common elements between two lists using Sets.

Q14

Create nested Company Dictionary.

Print: - Departments - Employees - Employee count

Final Decision Guide

Need ordered and changeable data?
→ LIST

Need ordered but fixed data?
→ TUPLE

Need key-value mapping?
→ DICTIONARY

Need unique values and fast membership checks?
→ SET

Master these four collections thoroughly and you will be able to solve a large percentage of real-world Python programming problems.

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