1st PUC Computer Science Chapter 10 Tuples and Dictionaries Notes | Class 11 Python Notes

A tuple is an ordered sequence that can contain elements of different data types. Tuple elements are written inside round brackets and separated by commas. Like strings and lists, tuple elements can be accessed using index values.

A dictionary is a mapping data type in Python in which information is stored as key-value pairs. Keys are used to access the corresponding values.

📌 Meaning of Tuple

Key Points

• Tuple elements are enclosed in round brackets ( ).
• Elements are separated by commas.
• Tuple elements have fixed positions.
• Indexing starts from 0.
• A tuple can contain different data types.
• A tuple can contain a list or another tuple as an element.

tuple1 = (1, 2, 3, 4, 5)
print(tuple1)

tuple2 = ('Economics', 87, 'Accountancy', 89.6)
print(tuple2)

tuple3 = (10, 20, 30, [40, 50])
print(tuple3)

tuple4 = (1, 2, 3, 4, 5, (10, 20))
print(tuple4)

📌 Single Element Tuple

If a tuple contains only one element, a comma must follow the element. Without the comma, Python treats the expression as an ordinary value.

tuple5 = (20)
print(type(tuple5))

tuple5 = (20,)
print(type(tuple5))

Tuple Without Parentheses

seq = 1, 2, 3
print(type(seq))
print(seq)

A comma-separated sequence without parentheses is also treated as a tuple.

Tuple elements can be accessed using indexing and slicing, similar to lists and strings.

tuple1 = (2, 4, 6, 8, 10, 12)

print(tuple1[0])
print(tuple1[3])
print(tuple1[-1])
print(tuple1[1+4])

tuple1 = (1, 2, 3, 4, 5)
tuple1[4] = 10

An attempt to assign a new value to an existing tuple position results in a TypeError.

Mutable Element Inside a Tuple

Although the tuple itself is immutable, an element inside it may be a mutable object such as a list.

tuple2 = (1, 2, 3, [8, 9])
tuple2[3][1] = 10

print(tuple2)

Here the list inside the tuple can be modified.

tuple1 = (1, 3, 5, 7, 9)
tuple2 = (2, 4, 6, 8, 10)

tuple3 = tuple1 + tuple2
print(tuple3)

Output:

(1, 3, 5, 7, 9, 2, 4, 6, 8, 10)

Extending a Tuple

tuple6 = (1, 2, 3, 4, 5)

tuple6 = tuple6 + (6,)
tuple6 = tuple6 + (7, 8, 9)

print(tuple6)

tuple1 = ('Hello', 'World')
print(tuple1 * 3)

Output:

('Hello', 'World', 'Hello', 'World', 'Hello', 'World')

tuple2 = ('Hello',)
print(tuple2 * 4)

Output:

('Hello', 'Hello', 'Hello', 'Hello')

The in operator checks whether an element is present in a tuple. It returns True when present and False otherwise.

tuple1 = ('Red', 'Green', 'Blue')

print('Green' in tuple1)
print('Green' not in tuple1)

Output:

True
False

Slicing can be applied to tuples in the same way as strings and lists.

tuple1 = (10, 20, 30, 40, 50, 60, 70, 80)

• The number of variables should match the number of values.
• Values are assigned according to their positions.
• Expressions on the right side are evaluated before assignment.

(num1, num2) = (10, 20)

print(num1)
print(num2)

record = ("Pooja", 40, "CS")
(name, rollNo, subject) = record

print(name)
print(rollNo)
print(subject)

(a, b, c, d) = (5, 6, 8)

Result: Not enough values to unpack.

Assignment with Expressions

(num3, num4) = (10 + 5, 20 + 5)

After evaluation, num3 = 15 and num4 = 25.

Nested tuples can be useful for storing records containing several related values, such as roll number, name and marks of students.

students = (
    (101, "Aman", 98),
    (102, "Geet", 95),
    (103, "Sahil", 87),
    (104, "Pawan", 79)
)

print("S_No  Roll_No  Name   Marks")

for i in range(len(students)):
    print(i + 1, students[i][0], students[i][1], students[i][2])

Program: Swapping Two Numbers Without a Temporary Variable

num1 = int(input("Enter the first number: "))
num2 = int(input("Enter the second number: "))

print("\nNumbers before swapping:")
print("First Number:", num1)
print("Second Number:", num2)

(num1, num2) = (num2, num1)

print("\nNumbers after swapping:")
print("First Number:", num1)
print("Second Number:", num2)

Program: Area and Circumference of a Circle Using a Function

def circle(r):
    area = 3.14 * r * r
    circumference = 2 * 3.14 * r
    return (area, circumference)

radius = int(input("Enter radius of circle: "))

area, circumference = circle(radius)

print("Area of circle is:", area)
print("Circumference of circle is:", circumference)

Program: Store n Numbers in a Tuple and Find Maximum & Minimum

numbers = tuple()

n = int(input("How many numbers do you want to enter?: "))

for i in range(n):
    num = int(input())
    numbers = numbers + (num,)

print("\nThe numbers in the tuple are:")
print(numbers)

print("The maximum number is:")
print(max(numbers))

print("The minimum number is:")
print(min(numbers))

• A key is separated from its value by a colon :.
• Consecutive items are separated by commas.
• Dictionary items are accessed using keys.
• Keys must be unique.
• Keys should be of an immutable type such as number, string or tuple.
• Values can be repeated and can be of different data types.

Empty Dictionary

dict1 = {}
print(dict1)

dict2 = dict()
print(dict2)

Dictionary with Data

dict3 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

print(dict3)

Unlike strings, lists and tuples, dictionary items are accessed using their keys rather than relative positions.

dict3 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

print(dict3["Ram"])
print(dict3["Sangeeta"])

Output:

89
85

print(dict3["Shyam"])

Result: KeyError.

10.8.1 Adding a New Item

dict1 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

dict1["Meena"] = 78

print(dict1)

10.8.2 Modifying an Existing Item

dict1["Suhel"] = 93.5
print(dict1)

10.9.1 Membership

The in operator checks whether a key is present in a dictionary.

dict1 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

print("Suhel" in dict1)
print("Suhel" not in dict1)

True
False

A dictionary can be traversed using a for loop.

Method 1 – Traverse Keys

dict1 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

for key in dict1:
    print(key, ":", dict1[key])

Method 2 – Traverse Key-Value Pairs

for key, value in dict1.items():
    print(key, ":", value)

Important Examples

dict1 = {
    "Mohan":95,
    "Ram":89,
    "Suhel":92,
    "Sangeeta":85
}

print(len(dict1))
print(dict1.keys())
print(dict1.values())
print(dict1.items())

print(dict1.get("Sangeeta"))

dict2 = {"Sohan":79, "Geeta":89}
dict1.update(dict2)

del dict1["Ram"]

dict1.clear()

Dictionary manipulation includes creating, accessing, adding, modifying, searching and deleting key-value pairs.

Dictionary Example – ODD

ODD = {
    1:"One",
    3:"Three",
    5:"Five",
    7:"Seven",
    9:"Nine"
}

print(ODD.keys())
print(ODD.values())
print(ODD.items())
print(len(ODD))

print(7 in ODD)
print(2 in ODD)

print(ODD.get(9))

del ODD[9]
print(ODD)

Program – Employee Names and Salaries

num = int(input("Enter the number of employees: "))

employee = {}
count = 1

while count <= num:
    name = input("Enter the name of the Employee: ")
    salary = int(input("Enter the salary: "))
    employee[name] = salary
    count += 1

print("\nEMPLOYEE_NAME\tSALARY")

for key in employee:
    print(key, "\t\t", employee[key])

Program – Count Character Occurrences in a String

st = input("Enter a string: ")
dic = {}

for ch in st:
    if ch in dic:
        dic[ch] += 1
    else:
        dic[ch] = 1

for key in dic:
    print(key, ":", dic[key])

Program – Convert Digits into Number Names

def convert(num):
    numberNames = {
        0:"Zero", 1:"One", 2:"Two", 3:"Three", 4:"Four",
        5:"Five", 6:"Six", 7:"Seven", 8:"Eight", 9:"Nine"
    }

    result = ""

    for ch in num:
        key = int(ch)
        result = result + " " + numberNames[key]

    return result

num = input("Enter any number: ")
result = convert(num)

print("The number is:", num)
print("The numberName is:", result)

The textbook presents a railway reservation system as an example of dividing a complex system into different subsystems. Each subsystem can be modelled using functions.

Tuple Output Questions

1. For tuple1 = (23,1,45,67,45,9,55,45) and tuple2 = (100,200), find the output of: tuple1.index(45), tuple1.count(45), tuple1 + tuple2, len(tuple2), max(tuple1), min(tuple1), sum(tuple2) and sorted(tuple1).

Dictionary Output Questions

Consider:

stateCapital = {
    "AndhraPradesh":"Hyderabad",
    "Bihar":"Patna",
    "Maharashtra":"Mumbai",
    "Rajasthan":"Jaipur"
}

Find the output of:

1. stateCapital.get("Bihar")
2. stateCapital.keys()
3. stateCapital.values()
4. stateCapital.items()
5. len(stateCapital)
6. "Maharashtra" in stateCapital
7. stateCapital.get("Assam")
8. del stateCapital["Rajasthan"] followed by printing the dictionary

Conceptual Questions

1. Explain why lists and tuples are ordered.
2. Show with an example how a function can return more than one value.
3. What advantages do tuples have over lists?
4. When should a tuple or dictionary be used? Give suitable programming situations.
5. Explain how a variable is rebuilt in the case of immutable data types.
6. Why does len(tuple1) produce an error when tuple1 = (5)?

Programming Problems

1. Read email IDs of n students and store them in a tuple. Create separate tuples for usernames and domain names.
2. Input names of n students into a tuple and check whether a given student is present.
3. Write a Python program to find the highest two values in a dictionary.
4. Write a Python program to create a dictionary from a string by counting letters.
5. Input friends’ names and phone numbers into a dictionary and perform display, add, delete, modify, search and sorted-display operations.

SMIS Student Records

Design a program using a dictionary where roll number can act as the key and an immutable data type containing student name and percentage can act as the value.

• Accept details of n students.
• Search for a student using roll number.
• Display the results of all students.
• Find the topper.
• Find subject toppers.

Banking System

• Open a savings bank account.
• Deposit money.
• Withdraw money while considering minimum balance.
• Take fixed-deposit amount and period and display maturity amount.
• Use functions and appropriate data types.

Quiz System

• Create an administrative user ID and password.
• Add, modify and delete questions.
• Register students before participation.
• Allow category selection.
• Display questions according to category.
• Maintain and display the score.

Indian Heritage Sites System

Create a system for storing and searching information about Indian World Heritage Sites.

• Site name
• Location
• District and State
• Year built
• Builder
• Purpose
• Website link, if available

Transportation Reservation System

Choose a mode of transportation and design a reservation system. A railway reservation system can be divided into subsystems such as train information, reservation information, staff/security/infrastructure, food service, billing service and other railway details.

Very Short Answer

1. Define tuple.
2. What is immutability?
3. Write the syntax for a single-element tuple.
4. What is tuple concatenation?
5. What is tuple repetition?
6. What is tuple slicing?
7. Define nested tuple.
8. Define dictionary.
9. What is a key-value pair?
10. What is dictionary mutability?
11. What is the use of keys()?
12. What is the use of values()?
13. What is the use of items()?
14. What is the use of get()?
15. What is the use of update()?

2-Mark / Short Answer Questions

1. Explain why tuples are immutable with an example.
2. Differentiate between list and tuple.
3. Explain positive and negative indexing in tuples.
4. Explain tuple concatenation with an example.
5. Explain tuple repetition with an example.
6. Explain tuple slicing with examples.
7. Explain tuple assignment.
8. Explain nested tuples.
9. Explain how a tuple can be used to return multiple values from a function.
10. Explain how dictionary items are accessed.
11. Explain how to add and modify dictionary items.
12. Explain dictionary traversal using a for loop.
13. Differentiate between get() and direct dictionary indexing.
14. Explain update(), del and clear().

Programming Questions

1. Write a program to swap two numbers without using a temporary variable.
2. Write a program to calculate area and circumference of a circle using a function returning a tuple.
3. Write a program to input n numbers into a tuple and find maximum and minimum.
4. Write a program to store employee names and salaries in a dictionary.
5. Write a program to count character occurrences in a string using a dictionary.
6. Write a function to convert digits into their corresponding number names.
7. Write a program to find the highest two values in a dictionary.
8. Write a program to create a dictionary from a string.

Difference Between List and Tuple

Difference Between Tuple and Dictionary

Tuples are immutable ordered sequences whose elements can be accessed through indexing and slicing. They support operations such as concatenation, repetition and membership checking. Python provides several functions and methods for processing tuples.

Dictionaries store information as key-value pairs. Keys are unique and are used to access values. Dictionaries are mutable and can be modified by adding, changing or deleting items. They can also be traversed using loops and manipulated using methods such as keys(), values(), items(), get(), update() and clear().