Class XI Computer Science – Unit 2: Computational Thinking and Programming-1 | 50 Advanced Python Programs

Topic 1: Flow of Control, Conditionals & Loops

Program 1: ATM PIN Verification with for-else

Scenario: Design an ATM system that allows a user three attempts to enter the correct PIN. After successful verification, the user can check balance, withdraw cash or exit.

balance = 10000.00
correct_pin = "1234"

for attempt in range(1, 4):

    pin = input(f"Attempt {attempt}/3 - Enter 4-digit PIN: ")

    if pin == correct_pin:

        print("\nVerification Successful!")

        while True:

            print("\n1. Check Balance")
            print("2. Withdraw Cash")
            print("3. Exit")

            choice = int(input("Select option: "))

            if choice == 1:
                print(f"Current Balance: Rs. {balance}")

            elif choice == 2:

                amt = float(input("Enter withdrawal amount: Rs. "))

                if amt > balance:
                    print("Insufficient balance!")

                elif amt <= 0:
                    print("Invalid amount!")

                else:
                    balance -= amt
                    print(f"Rs. {amt} withdrawn successfully.")

            elif choice == 3:
                print("Thank you for using our ATM.")
                break

            else:
                print("Invalid transaction option.")

        break

else:
    print("\n[ALERT] 3 incorrect attempts. Your card is blocked for 24 hours!")

Program 2: Movie Ticket Booking System

Scenario: Create a simple seat-booking system in which a customer can reserve three seats from a 3 × 4 seating arrangement.

rows, cols = 3, 4

seats = [["O" for _ in range(cols)] for _ in range(rows)]

booked = 0

while booked < 3:

    r = int(input("Enter row (0-2): "))
    c = int(input("Enter column (0-3): "))

    if 0 <= r < rows and 0 <= c < cols:

        if seats[r][c] == "O":
            seats[r][c] = "X"
            booked += 1
            print("Seat booked!")

        else:
            print("Seat already taken. Choose another.")

    else:
        print("Invalid seat number.")

for row in seats:
    print(row)

Program 3: Number Guessing Game with Limited Chances

import random

secret = random.randint(1, 50)

chances = 5

while chances > 0:

    guess = int(input(
        f"Guess the number ({chances} chances left): "
    ))

    if guess == secret:
        print("Correct! You win!")
        break

    elif guess < secret:
        print("Too low!")

    else:
        print("Too high!")

    chances -= 1

else:
    print(f"Out of chances! The number was {secret}.")

Program 4: Electricity Bill Calculator

units = float(input("Enter units consumed: "))

if units <= 100:
    bill = units * 3.5

elif units <= 300:
    bill = 100 * 3.5 + (units - 100) * 5

else:
    bill = 100 * 3.5 + 200 * 5 + (units - 300) * 7

surcharge = bill * 0.10 if bill > 1000 else 0

print(f"Total Bill: Rs. {bill + surcharge:.2f}")

Program 5: Multiplication Table Generator

n = int(input("Enter number: "))

for i in range(1, 11):
    print(f"{n} x {i:2} = {n*i:3}")

Program 6: Password Strength Checker

pwd = input("Enter password: ")

has_upper = has_lower = has_digit = has_special = False

special_chars = "!@#$%^&*"

for ch in pwd:

    if ch.isupper():
        has_upper = True

    elif ch.islower():
        has_lower = True

    elif ch.isdigit():
        has_digit = True

    elif ch in special_chars:
        has_special = True

score = sum([
    has_upper,
    has_lower,
    has_digit,
    has_special,
    len(pwd) >= 8
])

levels = {
    5: "Very Strong",
    4: "Strong",
    3: "Moderate"
}

print(levels.get(score, "Weak"))

Program 7: Floyd's Triangle

n = int(input("Enter number of rows: "))

num = 1

for i in range(1, n + 1):

    for j in range(i):

        print(num, end=" ")

        num += 1

    print()

Program 8: Simple Interest and Compound Interest Comparison

p = float(input("Principal: "))
r = float(input("Rate: "))
years = int(input("Years: "))

si = p
ci = p

for y in range(1, years + 1):

    si += p * r / 100
    ci += ci * r / 100

    print(
        f"Year {y}: SI Balance={si:.2f}, "
        f"CI Balance={ci:.2f}"
    )

Program 9: Prime Numbers in a Range

start, end = 10, 50

for num in range(start, end + 1):

    if num < 2:
        continue

    is_prime = True

    for i in range(2, int(num ** 0.5) + 1):

        if num % i == 0:
            is_prime = False
            break

    if is_prime:
        print(num, end=" ")

Program 10: Vending Machine Simulation

items = {
    "Water": 20,
    "Chips": 30,
    "Soda": 35
}

print(items)

choice = input("Select item: ")

if choice in items:

    price = items[choice]

    paid = 0

    while paid < price:

        paid += int(
            input(
                f"Insert coin (Rs. {price-paid} remaining): "
            )
        )

    change = paid - price

    print(
        f"Dispensing {choice}. "
        f"Change returned: Rs. {change}"
    )

else:
    print("Item not available.")

Topic 2: Strings

Program 11: Sentence Case Converter

text = input("Enter paragraph: ")

sentences = text.split(". ")

result = ". ".join(
    s.strip().capitalize()
    for s in sentences
)

print(result)

Program 12: Caesar Cipher Encoder

text = input("Enter message: ")

shift = int(input("Enter shift value: "))

result = ""

for ch in text:

    if ch.isalpha():

        base = ord('A') if ch.isupper() else ord('a')

        result += chr(
            (ord(ch) - base + shift) % 26 + base
        )

    else:
        result += ch

print("Encrypted:", result)

Program 13: Word Frequency Counter

text = input("Enter text: ").lower()

words = text.split()

freq = {}

for w in words:

    w = w.strip(".,!?")

    freq[w] = freq.get(w, 0) + 1

for word, count in freq.items():

    print(f"{word}: {count}")

Program 14: Palindrome Phrase Checker

s = input("Enter phrase: ")

cleaned = "".join(
    ch.lower()
    for ch in s
    if ch.isalnum()
)

print(
    "Palindrome"
    if cleaned == cleaned[::-1]
    else "Not a Palindrome"
)

Program 15: Longest Word Finder

sentence = input("Enter sentence: ")

words = sentence.split()

longest = max(words, key=len)

print(
    f"Longest word: {longest} "
    f"({len(longest)} letters)"
)

Program 16: Vowel Removal

s = input("Enter string: ")

no_vowels = ""

for ch in s:

    if ch.lower() not in "aeiou":
        no_vowels += ch

print("Without vowels:", no_vowels)

Program 17: Anagram Checker

s1 = input("Enter first word: ").lower()

s2 = input("Enter second word: ").lower()

if sorted(s1) == sorted(s2):
    print("Anagrams")
else:
    print("Not Anagrams")

Program 18: Text Justification Formatter

paragraph = input("Enter text: ")

words = paragraph.split()

line = ""

for word in words:

    if len(line) + len(word) + 1 <= 20:

        line += word + " "

    else:

        print(line.strip().ljust(20, '.'))

        line = word + " "

print(line.strip().ljust(20, '.'))

Program 19: Separate Digits, Alphabets and Special Characters

s = input("Enter mixed string: ")

digits = ""
alphabets = ""
specials = ""

for ch in s:

    if ch.isdigit():
        digits += ch

    elif ch.isalpha():
        alphabets += ch

    else:
        specials += ch

print("Digits:", digits)
print("Alphabets:", alphabets)
print("Specials:", specials)

Program 20: Run-Length Encoding

s = input("Enter string: ")

encoded = ""

i = 0

while i < len(s):

    count = 1

    while i + 1 < len(s) and s[i] == s[i + 1]:

        i += 1
        count += 1

    encoded += s[i] + str(count)

    i += 1

print("Encoded:", encoded)

Topic 3: Lists

Program 21: Student Grade Management

students = [
    ["Aarav", 85],
    ["Diya", 45],
    ["Kabir", 72],
    ["Meera", 91]
]

for s in students:

    if s[1] >= 90:
        grade = "A"

    elif s[1] >= 75:
        grade = "B"

    elif s[1] >= 50:
        grade = "C"

    else:
        grade = "Fail"

    print(
        f"{s[0]}: {s[1]} marks -> Grade {grade}"
    )

Program 22: Matrix Addition

A = [
    [1, 2, 3],
    [4, 5, 6]
]

B = [
    [7, 8, 9],
    [1, 2, 3]
]

result = []

for i in range(len(A)):

    row = []

    for j in range(len(A[0])):

        row.append(A[i][j] + B[i][j])

    result.append(row)

print("Sum Matrix:", result)

Program 23: Remove Duplicates while Preserving Order

L = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3]

unique = []

for item in L:

    if item not in unique:
        unique.append(item)

print("Unique elements:", unique)

Program 24: Second Largest Element

L = [23, 45, 12, 67, 34, 89, 2]

largest = second = float('-inf')

for num in L:

    if num > largest:

        second = largest
        largest = num

    elif num > second and num != largest:

        second = num

print("Second Largest:", second)

Program 25: Rotate a List by K Positions

L = [1, 2, 3, 4, 5, 6, 7]

k = int(input("Enter rotation count: ")) % len(L)

rotated = L[k:] + L[:k]

print("Rotated List:", rotated)

Program 26: Merge Two Sorted Lists

L1 = [1, 3, 5, 7]
L2 = [2, 4, 6, 8]

merged = []

i = j = 0

while i < len(L1) and j < len(L2):

    if L1[i] < L2[j]:

        merged.append(L1[i])
        i += 1

    else:

        merged.append(L2[j])
        j += 1

merged.extend(L1[i:])
merged.extend(L2[j:])

print("Merged List:", merged)

Program 27: Matrix Transpose

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

transpose = [
    [matrix[j][i] for j in range(len(matrix))]
    for i in range(len(matrix[0]))
]

print("Transpose:", transpose)

Program 28: Sales Data Analysis

sales = [
    ("Jan", 45000),
    ("Feb", 52000),
    ("Mar", 38000),
    ("Apr", 61000)
]

amounts = [s[1] for s in sales]

best = max(sales, key=lambda x: x[1])

worst = min(sales, key=lambda x: x[1])

print(f"Best Month: {best[0]} (Rs.{best[1]})")

print(f"Worst Month: {worst[0]} (Rs.{worst[1]})")

print(
    f"Average Sales: "
    f"Rs.{sum(amounts)/len(amounts):.2f}"
)

Program 29: Bubble Sort

L = [64, 34, 25, 12, 22, 11, 90]

n = len(L)

for i in range(n - 1):

    for j in range(n - 1 - i):

        if L[j] > L[j + 1]:

            L[j], L[j + 1] = L[j + 1], L[j]

print("Sorted List:", L)

Program 30: Inventory Stock Alert System

inventory = [
    {"item": "Pen", "qty": 5},
    {"item": "Notebook", "qty": 25},
    {"item": "Eraser", "qty": 2}
]

for stock in inventory:

    if stock["qty"] < 10:

        print(
            f"LOW STOCK ALERT: "
            f"{stock['item']} - only {stock['qty']} left!"
        )

    else:

        print(
            f"{stock['item']}: "
            f"Stock OK ({stock['qty']})"
        )

Topic 4: Tuples

Program 31: Coordinate Distance Calculator

import math

p1 = (2, 3)
p2 = (7, 9)

distance = math.sqrt(
    (p2[0] - p1[0]) ** 2 +
    (p2[1] - p1[1]) ** 2
)

print(f"Distance: {distance:.2f}")

Program 32: Employee Records Using Tuple of Tuples

employees = (
    ("Raj", "Manager", 75000),
    ("Priya", "Developer", 62000),
    ("Aman", "Intern", 20000)
)

for name, role, salary in employees:

    bonus = salary * 0.1 if role != "Intern" else 0

    print(
        f"{name} ({role}): "
        f"Bonus = Rs.{bonus}"
    )

Program 33: Highest and Lowest Salary

records = (
    ("Aarav", 55000),
    ("Diya", 72000),
    ("Kabir", 48000)
)

highest = max(records, key=lambda x: x[1])

lowest = min(records, key=lambda x: x[1])

print("Highest paid:", highest)

print("Lowest paid:", lowest)

Program 34: Swapping Values Using Tuple Unpacking

a, b, c = 10, 20, 30

a, b, c = c, a, b

print(f"a={a}, b={b}, c={c}")

Program 35: Tuple-Based Stack for Bracket Matching

expr = input("Enter expression: ")

stack = ()

balanced = True

for ch in expr:

    if ch == '(':

        stack += (ch,)

    elif ch == ')':

        if len(stack) == 0:

            balanced = False
            break

        stack = stack[:-1]

print(
    "Balanced"
    if balanced and len(stack) == 0
    else "Not Balanced"
)

Program 36: Convert List of Tuples to Dictionary

data = [
    ("Math", 88),
    ("Science", 92),
    ("English", 75)
]

subject_marks = dict(data)

print(subject_marks)

print(
    "Highest scoring subject:",
    max(subject_marks, key=subject_marks.get)
)

Topic 5: Dictionaries

Program 37: Contact Book Manager

contacts = {}

while True:

    print("\n1.Add 2.Search 3.Delete 4.Exit")

    ch = int(input("Choice: "))

    if ch == 1:

        name = input("Name: ")

        contacts[name] = input("Phone: ")

    elif ch == 2:

        name = input("Search name: ")

        print(
            contacts.get(name, "Not found")
        )

    elif ch == 3:

        name = input("Delete name: ")

        contacts.pop(name, None)

        print("Deleted (if existed).")

    elif ch == 4:

        break

print("Final Contacts:", contacts)

Program 38: Word Frequency Using Dictionary

text = (
    "the quick brown fox jumps over "
    "the lazy dog the fox runs"
)

words = text.split()

freq = {}

for w in words:

    freq[w] = freq.get(w, 0) + 1

sorted_freq = dict(
    sorted(
        freq.items(),
        key=lambda x: x[1],
        reverse=True
    )
)

print(sorted_freq)

Program 39: Exam Result Dictionary

results = {

    "Aarav": {
        "Maths": 90,
        "Science": 85
    },

    "Diya": {
        "Maths": 78,
        "Science": 92
    }
}

for student, subjects in results.items():

    total = sum(subjects.values())

    print(
        f"{student}: "
        f"Total = {total}, "
        f"Average = {total / len(subjects):.2f}"
    )

Program 40: Merging Two Dictionaries

d1 = {
    "apple": 10,
    "banana": 5,
    "mango": 8
}

d2 = {
    "banana": 7,
    "grape": 12,
    "mango": 3
}

merged = d1.copy()

for key, value in d2.items():

    if key in merged:
        merged[key] += value

    else:
        merged[key] = value

print("Merged Inventory:", merged)

Program 41: Most Common Character

s = input("Enter string: ")

freq = {}

for ch in s:

    freq[ch] = freq.get(ch, 0) + 1

most_common = max(freq, key=freq.get)

print(
    f"Most frequent character: "
    f"'{most_common}' "
    f"({freq[most_common]} times)"
)

Program 42: Dictionary-Based Voting System

votes = {}

n = int(input("Number of votes: "))

for _ in range(n):

    candidate = input("Vote for: ")

    votes[candidate] = votes.get(candidate, 0) + 1

winner = max(votes, key=votes.get)

print("Vote Count:", votes)

print(
    f"Winner: {winner} "
    f"with {votes[winner]} votes"
)

Program 43: Employee Database Using setdefault()

emp = {}

emp.setdefault("E101", []).append("Raj")

emp.setdefault("E101", []).append("Developer")

emp.setdefault("E102", []).append("Priya")

print(emp)

Program 44: Grade Distribution Counter

marks = [
    45, 78, 92, 34, 67,
    88, 55, 23, 99, 60
]

grades = {
    "A": 0,
    "B": 0,
    "C": 0,
    "Fail": 0
}

for m in marks:

    if m >= 90:
        grades["A"] += 1

    elif m >= 75:
        grades["B"] += 1

    elif m >= 40:
        grades["C"] += 1

    else:
        grades["Fail"] += 1

print(grades)

Topic 6: Operators & Expressions

Program 45: BMI Calculator with Category Classification

weight = float(input("Weight (kg): "))

height = float(input("Height (m): "))

bmi = weight / height ** 2

category = (
    "Underweight" if bmi < 18.5 else
    "Normal" if bmi < 25 else
    "Overweight" if bmi < 30 else
    "Obese"
)

print(
    f"BMI: {bmi:.2f} -> {category}"
)

Program 46: Leap Year Checker

year = int(input("Enter year: "))

is_leap = (
    (year % 4 == 0 and year % 100 != 0)
    or
    (year % 400 == 0)
)

print(
    f"{year} is "
    f"{'a Leap Year' if is_leap else 'not a Leap Year'}"
)

Program 47: Temperature Conversion

scale = input(
    "Convert from (C/F): "
).upper()

temp = float(
    input("Enter temperature: ")
)

if scale in ("C", "c"):

    print(
        f"Fahrenheit: "
        f"{temp * 9 / 5 + 32:.2f}"
    )

elif scale in ("F", "f"):

    print(
        f"Celsius: "
        f"{(temp - 32) * 5 / 9:.2f}"
    )

else:

    print("Invalid scale")

Program 48: Calculator Using Augmented Assignment

result = 0

ops = [
    "+5",
    "-3",
    "*4",
    "//2",
    "**2"
]

for op in ops:

    if op.startswith("+"):

        value = int(op[1:])
        result += value

    elif op.startswith("-"):

        value = int(op[1:])
        result -= value

    elif op.startswith("**"):

        value = int(op[2:])
        result **= value

    elif op.startswith("*"):

        value = int(op[1:])
        result *= value

    elif op.startswith("//"):

        value = int(op[2:])
        result //= value

    print(
        f"After {op}: {result}"
    )

Topic 7: Modules — math, random and statistics

Program 49: Dice Rolling Simulator with Statistics

import random
import statistics

rolls = [
    random.randint(1, 6)
    for _ in range(20)
]

print("Rolls:", rolls)

print(
    "Mean:",
    statistics.mean(rolls)
)

print(
    "Median:",
    statistics.median(rolls)
)

print(
    "Mode:",
    statistics.mode(rolls)
)

Program 50: Circle and Sphere Geometry Calculator

import math

r = float(input("Enter radius: "))

area = math.pi * r ** 2

circumference = 2 * math.pi * r

volume = (4 / 3) * math.pi * r ** 3

print(
    f"Area: {area:.2f}"
)

print(
    f"Circumference: "
    f"{circumference:.2f}"
)

print(
    f"Sphere Volume: "
    f"{volume:.2f}"
)

print(
    f"Ceil of radius: "
    f"{math.ceil(r)}, "
    f"Floor: {math.floor(r)}"
)

Quick Revision: 50 Programs at a Glance

Board Examination & Practical Tips

Final Takeaway

Programming is not simply about remembering syntax. The objective is to analyse a problem, break it into smaller steps, select appropriate Python constructs and develop a logical solution.

These 50 programs provide a progressive practice set in which individual Python concepts are combined to solve real-world computational problems.