Definition of Dictionary:-

A collection of key and value pairs enclosed in curly brackets.

Syntax

dictionary_name[key] = new_value # Updating a single value

Example

Syntax

dictionary_name[key] = value

# Adding a new key-value

Example

Syntax

dictionary_name.update({key1: new_value1, key2: new_value2})

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• This updates an existing key’s value or adds a new key-value pair.
• It can also update multiple values at once.

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Example

Try this ! Exercise 1

What will be the output of the following code?

student = {"name": "Alice", "age": 20, "grade": "B"}

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# Updating an existing value

student["grade"] = "A"

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# Adding a new key-value pair

student["city"] = "New York"

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print(student)

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Try this ! Exercise 2

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Which of the following correctly adds multiple key-value pairs to a dictionary?

1. student["age", "grade"] = 21, "A“
2. student.update({"age": 21, "grade": "A"})
3. student.add("age", 21)

student.add("grade", "A")

4. student["age": 21, "grade": "A"]

Try this ! Exercise 3

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You have the following dictionary representing a book:

book = { "title": "Python Basics", "author": "John Doe", "price": 50 }

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1. Update the price of the book to 55.
2. Print the updated dictionary.

Try this ! Exercise 4

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Given the dictionary below:

employee = {"name": "Aisha","department": "IT","salary": 5000}

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1. Add a new key "position" with the value "Software Engineer".
2. Print the updated dictionary.

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Try this ! Exercise 5

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You have the following dictionary representing a student:

student = {"name": "Ali","age": 20,"course": "Mathematics“ }

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1. Update the "age" to 21 and the "course" to "Computer Science" in one operation.
2. Print the updated dictionary.

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Syntax

del dictionary_name[key] # Deletes a specific key

• Removes the specified key and its corresponding value.
• Raises a KeyError if the key does not exist.

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Example

Syntax

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removed_value = dictionary_name.pop(key, default_value)

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• Removes the key and returns its value.
• If the key does not exist, it returns default_value (if provided); otherwise, it raises a KeyError.

Example

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Syntax

dictionary_name.clear() # Removes all elements

• Removes all key-value pairs from the dictionary, making it an empty dictionary { }.

Example

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Try this ! Exercise 1

What will be the output of the following code?

student = {"name": "Ali", "age": 20, "course": "Math"}

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del student["age"]

print(student)

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A) {'name': 'Ali', 'age': 20, 'course': 'Math'}�B) {'name': 'Ali', 'course': 'Math'}�C) KeyError�D) {'name': 'Ali'}

Try this ! Exercise 2

What will be stored in the variable removed_value after executing the following code?

car = {"brand": "Toyota", "model": "Camry", "year": 2022}

removed_value = car.pop("model")

print(removed_value)

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A) "Toyota"�B) "Camry"�C) {"brand": "Toyota", "year": 2022}�D) KeyError

Try this ! Exercise 3

What happens when you apply the clear() method to a dictionary?

data = {"id": 101, "name": "John", "age": 25}

data.clear()

print(data)

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A) {'id': 101, 'name': 'John', 'age': 25}�B) {}�C) None�D) KeyError

Syntax

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if key in dictionary_name:

print("Key exists!")

• Checks if the key is present in the dictionary.
• Returns True if the key exists, otherwise False.

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Example

Try this ! Exercise 1

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What will be the output of the following code?

person = {"name": "John", "age": 30, "city": "New York"}

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if "age" in person:

print("Key exists!")

else:

print("Key does not exist!")

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Feature

Dictionary (dict)

Tuple (tuple)

Set (set)

Definition

Key-value pairs

Ordered collection of elements

Unordered collection of unique elements

Mutable?

✅ Yes (values can change, keys cannot)

❌ No (immutable)

✅ Yes (elements can be added/removed)

Ordered?

✅ Yes (Python 3.7+)

✅ Yes

❌ No

Duplicates Allowed?

❌ No (keys must be unique)

✅ Yes

❌ No

Access Method

By key (dict[key])

By index (tuple[index])

Cannot access by index (only iteration)

Common Use Cases

Storing structured data (e.g., JSON, records)

Fixed data that should not change (e.g., coordinates, database records)

Unique collections (e.g., removing duplicates, set operations)

Try this ! Exercise 1

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Which of the following statements is TRUE based on the characteristics of Dictionary, Tuple, and Set?

A) A tuple is mutable and allows modification after creation.�B) A dictionary allows duplicate keys.�C) A set is ordered and supports indexing.�D) A dictionary allows value modification, but keys must remain unique.

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Try this ! Exercise 2

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Which of the following statements correctly describes how elements are accessed in different data structures?

A) A dictionary accesses values using keys (dict[key]).�B) A tuple accesses values using keys.�C) A set allows direct access using an index like a list.�D) A dictionary and a set both support accessing elements by index.

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Try this ! Exercise 3

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Which of the following data structures allows duplicate elements?

A) Dictionary (dict)�B) Tuple (tuple)�C) Set (set)�D) Both Dictionary and Set

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