20 Important Python Programs for CBSE Class 12 Practical Exam 2026-27

The CBSE Class 12 Computer Science practical exam carries 30 marks. Here are the most frequently asked Python programs you must practice.

Program 1: Read and Display a Text File

def read_file():
    f = open("story.txt", "r")
    content = f.read()
    print(content)
    f.close()

read_file()

Program 2: Count Lines Starting with a Specific Letter

def count_lines(filename, letter):
    f = open(filename, "r")
    count = 0
    for line in f:
        if line.strip().startswith(letter):
            count += 1
    f.close()
    return count

result = count_lines("story.txt", "T")
print("Lines starting with T:", result)

Program 3: Count Words in a Text File

def count_words(filename):
    f = open(filename, "r")
    content = f.read()
    words = content.split()
    f.close()
    return len(words)

print("Total words:", count_words("story.txt"))

Program 4: Copy Lines Containing a Word to Another File

def copy_lines(source, dest, word):
    f1 = open(source, "r")
    f2 = open(dest, "w")
    for line in f1:
        if word in line:
            f2.write(line)
    f1.close()
    f2.close()

copy_lines("story.txt", "output.txt", "Python")

Program 5: Read and Write CSV File

import csv

# Writing
with open("students.csv", "w", newline="") as f:
    writer = csv.writer(f)
    writer.writerow(["Name", "Marks", "Grade"])
    writer.writerow(["Aman", 85, "A"])
    writer.writerow(["Priya", 92, "A+"])

# Reading
with open("students.csv", "r") as f:
    reader = csv.reader(f)
    for row in reader:
        print(row)

Output:

['Name', 'Marks', 'Grade']
['Aman', '85', 'A']
['Priya', '92', 'A+']

Program 6: Binary File, Write and Read Using Pickle

import pickle

# Writing
students = {"Aman": 85, "Priya": 92, "Rahul": 67}
with open("students.dat", "wb") as f:
    pickle.dump(students, f)

# Reading
with open("students.dat", "rb") as f:
    data = pickle.load(f)
    print(data)

Output:

{'Aman': 85, 'Priya': 92, 'Rahul': 67}

Program 7: Stack Using List, Push and Pop

stack = []

def push(element):
    stack.append(element)
    print(f"Pushed: {element}")

def pop():
    if not stack:
        print("Stack Underflow!")
    else:
        return stack.pop()

def display():
    if not stack:
        print("Stack is empty")
    else:
        print("Stack:", stack[::-1])

push(10)
push(20)
push(30)
display()
print("Popped:", pop())
display()

Output:

Pushed: 10
Pushed: 20
Pushed: 30
Stack: [30, 20, 10]
Popped: 30
Stack: [20, 10]

Program 8: Count Uppercase, Lowercase, Digits, Special Characters

def count_chars(filename):
    upper = lower = digits = special = 0
    f = open(filename, "r")
    content = f.read()
    for ch in content:
        if ch.isupper():
            upper += 1
        elif ch.islower():
            lower += 1
        elif ch.isdigit():
            digits += 1
        elif ch != ' ' and ch != '\n':
            special += 1
    f.close()
    print(f"Uppercase: {upper}")
    print(f"Lowercase: {lower}")
    print(f"Digits: {digits}")
    print(f"Special: {special}")

count_chars("story.txt")

Program 9: Python-MySQL Connectivity, Create and Insert

import mysql.connector

conn = mysql.connector.connect(
    host="localhost",
    user="root",
    password="password",
    database="school"
)
cursor = conn.cursor()

cursor.execute("CREATE TABLE IF NOT EXISTS students (rollno INT PRIMARY KEY, name VARCHAR(50), marks INT)")
cursor.execute("INSERT INTO students VALUES (1, 'Aman', 85)")
cursor.execute("INSERT INTO students VALUES (2, 'Priya', 92)")
conn.commit()
print("Records inserted successfully")

cursor.close()
conn.close()

Program 10: Python-MySQL, Fetch and Display Records

import mysql.connector

conn = mysql.connector.connect(
    host="localhost",
    user="root",
    password="password",
    database="school"
)
cursor = conn.cursor()

cursor.execute("SELECT * FROM students WHERE marks > 80")
rows = cursor.fetchall()

for row in rows:
    print(f"Roll: {row[0]}, Name: {row[1]}, Marks: {row[2]}")

cursor.close()
conn.close()

Output:

Roll: 1, Name: Aman, Marks: 85
Roll: 2, Name: Priya, Marks: 92

Program 11: Random Number Generator

import random

for i in range(5):
    print(random.randint(1, 100), end=" ")

Program 12: Search in a Text File

def search_word(filename, word):
    f = open(filename, "r")
    line_num = 0
    found = False
    for line in f:
        line_num += 1
        if word in line:
            print(f"Found '{word}' in line {line_num}: {line.strip()}")
            found = True
    if not found:
        print(f"'{word}' not found in file")
    f.close()

search_word("story.txt", "Python")

Program 13: Replace a Word in a File

def replace_word(filename, old, new):
    f = open(filename, "r")
    content = f.read()
    f.close()

    content = content.replace(old, new)

    f = open(filename, "w")
    f.write(content)
    f.close()
    print(f"Replaced '{old}' with '{new}'")

replace_word("story.txt", "Python", "PYTHON")

Program 14: Bubble Sort

def bubble_sort(arr):
    n = len(arr)
    for i in range(n - 1):
        for j in range(n - 1 - i):
            if arr[j] > arr[j + 1]:
                arr[j], arr[j + 1] = arr[j + 1], arr[j]
    return arr

numbers = [64, 34, 25, 12, 22, 11, 90]
print("Sorted:", bubble_sort(numbers))

Output:

Sorted: [11, 12, 22, 25, 34, 64, 90]

Program 15: Binary Search

def binary_search(arr, target):
    low = 0
    high = len(arr) - 1
    while low <= high:
        mid = (low + high) // 2
        if arr[mid] == target:
            return mid
        elif arr[mid] < target:
            low = mid + 1
        else:
            high = mid - 1
    return -1

numbers = [10, 20, 30, 40, 50, 60, 70]
pos = binary_search(numbers, 40)
print(f"Found at index: {pos}")

Output:

Found at index: 3

Program 16: Write and Read Student Records Using Binary File

import pickle

def write_students():
    f = open("students.dat", "wb")
    while True:
        roll = int(input("Enter roll: "))
        name = input("Enter name: ")
        marks = float(input("Enter marks: "))
        record = [roll, name, marks]
        pickle.dump(record, f)
        choice = input("Add more? (y/n): ")
        if choice.lower() == 'n':
            break
    f.close()

def read_students():
    f = open("students.dat", "rb")
    try:
        while True:
            record = pickle.load(f)
            print(record)
    except EOFError:
        pass
    f.close()

Program 17: Count Vowels and Consonants in a File

def count_vowels_consonants(filename):
    vowels = consonants = 0
    f = open(filename, "r")
    content = f.read()
    for ch in content.lower():
        if ch.isalpha():
            if ch in 'aeiou':
                vowels += 1
            else:
                consonants += 1
    f.close()
    print(f"Vowels: {vowels}, Consonants: {consonants}")

count_vowels_consonants("story.txt")

Program 18: Exception Handling

def safe_divide():
    try:
        a = int(input("Enter first number: "))
        b = int(input("Enter second number: "))
        result = a / b
        print(f"Result: {result}")
    except ZeroDivisionError:
        print("Error: Cannot divide by zero!")
    except ValueError:
        print("Error: Please enter valid numbers!")
    finally:
        print("Program completed")

safe_divide()

Program 19: Insertion Sort

def insertion_sort(arr):
    for i in range(1, len(arr)):
        key = arr[i]
        j = i - 1
        while j >= 0 and arr[j] > key:
            arr[j + 1] = arr[j]
            j -= 1
        arr[j + 1] = key
    return arr

numbers = [12, 11, 13, 5, 6]
print("Sorted:", insertion_sort(numbers))

Output:

Sorted: [5, 6, 11, 12, 13]

Program 20: MySQL, Update and Delete

import mysql.connector

conn = mysql.connector.connect(
    host="localhost", user="root",
    password="password", database="school"
)
cursor = conn.cursor()

# Update
cursor.execute("UPDATE students SET marks = 95 WHERE name = 'Aman'")
conn.commit()
print(f"Rows updated: {cursor.rowcount}")

# Delete
cursor.execute("DELETE FROM students WHERE marks < 50")
conn.commit()
print(f"Rows deleted: {cursor.rowcount}")

cursor.close()
conn.close()

Tips for the Practical Exam

1. Always write comments - The examiner looks for them
2. Test with sample data - Run your program before submitting
3. Handle errors - Use try-except where applicable
4. Use meaningful variable names - Not a, b, c
5. Practice file operations - Text, binary, and CSV

Practice these programs daily. The CBSE practical exam is 30 marks, do not take it lightly.