1from datetime import date
2 
3entry = input("Dear diary: ")
4with open("diary.txt", "a", encoding="utf-8") as f:
5    f.write(f"== {date(2026, 10, 8):%d %b %Y} ==\n{entry}\n")
6 
7with open("diary.txt", encoding="utf-8") as f:
8    text = f.read()
9print(text)
10print("Entries so far:", text.count("== "))

1import csv
2students = [(1, "Aman"), (2, "Priya"), (3, "Rahul"), (4, "Sneha"), (5, "Kiran")]
3day = "08-10-2026"
4present = 0
5with open("attendance_9A.csv", "w", newline="", encoding="utf-8") as f:
6    w = csv.writer(f)
7    w.writerow(["date", "roll", "name", "status"])
8    for roll, name in students:
9        s = input(f"{roll} {name} (P/A): ").strip().upper()
10        w.writerow([day, roll, name, s])
11        present += s == "P"
12print(f"Present: {present}, Absent: {len(students) - present}")

1import csv
2 
3def grade(p):
4    return "A" if p >= 80 else "B" if p >= 60 else "C" if p >= 40 else "F"
5 
6results = []
7with open("marks.csv", encoding="utf-8") as f:
8    for r in csv.DictReader(f):
9        total = int(r["maths"]) + int(r["science"]) + int(r["english"])
10        pct = round(total / 3, 1)
11        results.append({"name": r["name"], "total": total, "percent": pct, "grade": grade(pct)})
12 
13with open("result.csv", "w", newline="", encoding="utf-8") as f:
14    w = csv.DictWriter(f, fieldnames=["name", "total", "percent", "grade"])
15    w.writeheader()
16    w.writerows(results)
17 
18top = max(results, key=lambda r: r["total"])
19print(f"{len(results)} results written. Topper: {top['name']} ({top['percent']}%)")

1import json, os
2 
3DEFAULTS = {"language": "English", "sound": True, "difficulty": "easy", "high_score": 0}
4if os.path.exists("config.json"):
5    with open("config.json") as f:
6        config = json.load(f)
7    print("Loaded saved settings")
8else:
9    config = DEFAULTS.copy()
10    print("No settings found, using defaults")
11 
12config["difficulty"] = input("Difficulty (easy/medium/hard): ")
13config["high_score"] = max(config["high_score"], 85)
14 
15with open("config.json", "w") as f:
16    json.dump(config, f, indent=2)
17print("Saved:", config)

1import json, os
2FILE = "contacts.json"
3 
4def load():
5    if not os.path.exists(FILE):
6        return {}
7    with open(FILE, encoding="utf-8") as f:
8        return json.load(f)
9 
10def save(book):
11    with open(FILE, "w", encoding="utf-8") as f:
12        json.dump(book, f, indent=2, sort_keys=True)
13 
14book = load()
15print(f"{len(book)} contacts loaded")
16while True:
17    c = input("1 Add  2 Search  3 List  4 Quit: ")
18    if c == "1":
19        name = input("Name: ").title()
20        book[name] = input("Phone: ")
21        save(book)
22    elif c == "2":
23        name = input("Search: ").title()
24        print(" ", book.get(name, "Not found"))
25    elif c == "3":
26        for n, p in sorted(book.items()):
27            print(f"  {n:<8} {p}")
28    else:
29        break

1def get_int(prompt, low, high):
2    while True:
3        try:
4            value = int(input(prompt))
5            if low <= value <= high:
6                return value
7            print(f"  Please enter a number from {low} to {high}.")
8        except ValueError:
9            print("  That is not a whole number.")
10 
11class_no = get_int("Class (1-12): ", 1, 12)
12roll = get_int("Roll number (1-60): ", 1, 60)
13print(f"Registered: class {class_no}, roll {roll}")

1while True:
2    op = input("Operator (+ - * /) or q: ")
3    if op == "q":
4        break
5    try:
6        a = float(input("  First number: "))
7        b = float(input("  Second number: "))
8        if op == "+": r = a + b
9        elif op == "-": r = a - b
10        elif op == "*": r = a * b
11        elif op == "/": r = a / b
12        else:
13            raise ValueError(f"unknown operator {op}")
14        print(f"  = {r:g}")
15    except ZeroDivisionError:
16        print("  Cannot divide by zero")
17    except ValueError as e:
18        print("  Error:", e)
19print("Bye!")

1def load_students(path):
2    try:
3        with open(path, encoding="utf-8") as f:
4            names = f.read().splitlines()
5    except FileNotFoundError:
6        print(f"{path} not found. Creating it with sample data.")
7        names = ["Aman", "Priya", "Rahul"]
8        with open(path, "w", encoding="utf-8") as f:
9            f.write("\n".join(names))
10    else:
11        print(f"Loaded {len(names)} students from {path}")
12    finally:
13        print("Startup complete")
14    return names
15 
16print(load_students("students.txt"))
17print(load_students("students.txt"))

1class InsufficientBalance(Exception): pass
2class DailyLimitExceeded(Exception): pass
3 
4balance, withdrawn_today, LIMIT = 12000, 0, 10000
5errors = []
6 
7def withdraw(amount):
8    global balance, withdrawn_today
9    if amount > balance:
10        raise InsufficientBalance(f"need {amount}, have {balance}")
11    if withdrawn_today + amount > LIMIT:
12        raise DailyLimitExceeded(f"limit {LIMIT}, used {withdrawn_today}")
13    balance -= amount
14    withdrawn_today += amount
15 
16for amt in [4000, 5000, 3000, 15000]:
17    try:
18        withdraw(amt)
19        print(f"OK  {amt:>6}  balance {balance}")
20    except (InsufficientBalance, DailyLimitExceeded) as e:
21        errors.append(f"{type(e).__name__}: {e}")
22        print(f"NO  {amt:>6}  {type(e).__name__}")
23print("Error log:", *errors, sep="\n  ")

1raw = ["Aman,78", "Priya,95", "Rahul,abc", "Sneha", "Kiran,105", "Dev,64"]
2good, bad = {}, []
3for line in raw:
4    try:
5        name, marks = line.split(",")
6        marks = int(marks)
7        if not 0 <= marks <= 100:
8            raise ValueError("marks out of range")
9        good[name] = marks
10    except ValueError as e:
11        bad.append((line, str(e)))
12 
13assert len(good) + len(bad) == len(raw), "lost a record!"
14print("Valid:", good)
15print("Rejected:")
16for line, why in bad:
17    print(f"  {line!r:<12} -> {why}")

1class Student:
2    def __init__(self, name, cls):
3        self.name, self.cls = name, cls
4        self.marks = {}
5 
6    def add_marks(self, subject, m):
7        self.marks[subject] = m
8 
9    def percentage(self):
10        return sum(self.marks.values()) / len(self.marks)
11 
12    def grade(self):
13        p = self.percentage()
14        return "A" if p >= 80 else "B" if p >= 60 else "C" if p >= 33 else "F"
15 
16    def __str__(self):
17        return f"{self.name} ({self.cls}): {self.percentage():.1f}% grade {self.grade()}"
18 
19s = Student("Ankita Toppo", "10A")
20for sub, m in [("Maths", 88), ("Science", 79), ("English", 91), ("Hindi", 84)]:
21    s.add_marks(sub, m)
22print(s)
23print("Best subject:", max(s.marks, key=s.marks.get))

1class SavingsAccount:
2    MIN_BALANCE = 500
3 
4    def __init__(self, owner, acc_no, balance=0):
5        self.owner, self.acc_no, self.balance = owner, acc_no, balance
6        self.tx = []
7 
8    def deposit(self, amt):
9        self.balance += amt
10        self.tx.append(("CR", amt))
11 
12    def withdraw(self, amt):
13        if self.balance - amt < self.MIN_BALANCE:
14            print(f"Declined: must keep Rs {self.MIN_BALANCE}")
15            return
16        self.balance -= amt
17        self.tx.append(("DR", amt))
18 
19    def add_interest(self, rate=3.5):
20        i = round(self.balance * rate / 100, 2)
21        self.deposit(i)
22 
23    def statement(self):
24        print(f"A/c {self.acc_no} | {self.owner}")
25        for kind, amt in self.tx[-5:]:
26            print(f"  {kind}  {amt:>10,.2f}")
27        print(f"  Balance {self.balance:>8,.2f}")
28 
29a = SavingsAccount("Ravi Mahato", "XX4521", 1000)
30a.deposit(5000)
31a.withdraw(5800)
32a.withdraw(2500)
33a.add_interest()
34a.statement()

1class Product:
2    def __init__(self, name, price):
3        self.name, self.price = name, price
4    def __repr__(self):
5        return f"{self.name}@{self.price}"
6 
7class Cart:
8    def __init__(self):
9        self.items = {}            # name -> (product, qty)
10    def add(self, product, qty=1):
11        old = self.items.get(product.name, (product, 0))[1]
12        self.items[product.name] = (product, old + qty)
13    def remove(self, name):
14        self.items.pop(name, None)
15    def total(self):
16        t = sum(p.price * q for p, q in self.items.values())
17        return t * 0.95 if t > 2000 else t
18    def show(self):
19        for p, q in self.items.values():
20            print(f"  {p.name:<12} x{q}  Rs {p.price * q}")
21        print(f"  Payable: Rs {self.total():.2f}")
22 
23bag, shoes, bottle = Product("School bag", 899), Product("Shoes", 1250), Product("Bottle", 199)
24cart = Cart()
25cart.add(bag); cart.add(bottle, 2); cart.add(shoes); cart.remove("Bottle"); cart.add(bottle)
26cart.show()

1class Phone:
2    DRAIN = {"YouTube": 0.5, "WhatsApp": 0.2, "Game": 0.8}
3 
4    def __init__(self, model, battery=60):
5        self.model, self.battery, self.is_on = model, battery, True
6 
7    def use(self, app, minutes):
8        if not self.is_on:
9            print(f"{self.model} is off. Charge it first!")
10            return
11        self.battery = max(0, self.battery - self.DRAIN[app] * minutes)
12        if self.battery == 0:
13            self.is_on = False
14        self.status(f"{app} {minutes} min")
15 
16    def charge(self, minutes):
17        self.battery = min(100, self.battery + minutes)
18        self.is_on = True
19        self.status(f"charged {minutes} min")
20 
21    def status(self, action):
22        bar = "#" * int(self.battery // 10)
23        print(f"{action:<18} [{bar:<10}] {self.battery:5.1f}% {'ON' if self.is_on else 'OFF'}")
24 
25p = Phone("Galaxy M14")
26p.use("YouTube", 40); p.use("Game", 60); p.use("WhatsApp", 30); p.charge(45); p.use("Game", 30)