File Handling

with open("message.txt", "w", encoding="utf-8") as file:
    file.write("Hello Python")

with open("message.txt", "r", encoding="utf-8") as file:
    content = file.read()

print(content)

with open("message.txt", "r", encoding="utf-8") as file:
    for line in file:
        print(line.strip())

with open("message.txt", "r", encoding="utf-8") as file:
    print(file.readline().strip())

with open("message.txt", "r", encoding="utf-8") as file:
    lines = file.readlines()

print(lines)

with open("message.txt", "a", encoding="utf-8") as file:
    file.write("\nThis is a new line.")

lines = ["Python\n", "SQL\n", "Power BI\n"]

with open("courses.txt", "w", encoding="utf-8") as file:
    file.writelines(lines)

with open("courses.txt", "r", encoding="utf-8") as file:
    count = sum(1 for line in file)

print("Lines:", count)

with open("message.txt", "r", encoding="utf-8") as file:
    text = file.read()

print("Words:", len(text.split()))

with open("message.txt", "r", encoding="utf-8") as file:
    text = file.read().lower()

print(text.split().count("python"))

with open("message.txt", "r", encoding="utf-8") as file:
    print("Start:", file.tell())
    print(file.read(5))
    print("After read:", file.tell())
    file.seek(0)
    print("Again:", file.read(5))

with open("message.txt", "r", encoding="utf-8") as source:
    content = source.read()

with open("backup.txt", "w", encoding="utf-8") as target:
    target.write(content)

try:
    with open("missing.txt", "r", encoding="utf-8") as file:
        print(file.read())
except FileNotFoundError:
    print("File not found")

import csv

rows = [
    ["ID", "Name", "Marks"],
    [1, "Ravi", 85],
    [2, "Anita", 92]
]

with open("students.csv", "w", newline="", encoding="utf-8") as file:
    writer = csv.writer(file)
    writer.writerows(rows)

import csv

with open("students.csv", "r", newline="", encoding="utf-8") as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

import csv

with open("students.csv", "r", newline="", encoding="utf-8") as file:
    reader = csv.DictReader(file)
    for row in reader:
        print(row["Name"], row["Marks"])

import csv

records = [
    {"ID": 1, "Name": "Ravi", "Marks": 85},
    {"ID": 2, "Name": "Anita", "Marks": 92}
]

with open("students2.csv", "w", newline="", encoding="utf-8") as file:
    writer = csv.DictWriter(file, fieldnames=["ID", "Name", "Marks"])
    writer.writeheader()
    writer.writerows(records)

import json

student = {"name": "Ravi", "age": 21, "course": "Python"}
text = json.dumps(student, indent=2)

print(text)

import json

text = '{"name": "Ravi", "age": 21}'
student = json.loads(text)

print(student["name"])

import json

data = {
    "name": "Anita",
    "skills": ["Python", "SQL"]
}

with open("student.json", "w", encoding="utf-8") as file:
    json.dump(data, file, indent=2)

import json

with open("student.json", "r", encoding="utf-8") as file:
    data = json.load(file)

print(data)

import json

with open("student.json", "r", encoding="utf-8") as file:
    data = json.load(file)

data["name"] = "Anita Sharma"

with open("student.json", "w", encoding="utf-8") as file:
    json.dump(data, file, indent=2)

try:
    age = int(input("Enter age: "))
    print("Age:", age)
except ValueError:
    print("Please enter a valid integer.")

try:
    a = int(input("Enter numerator: "))
    b = int(input("Enter denominator: "))
    print(a / b)
except ZeroDivisionError:
    print("Cannot divide by zero.")
except ValueError:
    print("Enter numbers only.")

try:
    number = int(input("Enter a number: "))
except ValueError:
    print("Invalid input")
else:
    print("Square:", number ** 2)
finally:
    print("Program finished")

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

if age < 0:
    raise ValueError("Age cannot be negative")

print("Valid age:", age)

class InsufficientBalanceError(Exception):
    pass

balance = 1000
withdraw = 1500

if withdraw > balance:
    raise InsufficientBalanceError("Insufficient balance")

import csv

total = 0
count = 0

with open("students.csv", "r", newline="", encoding="utf-8") as file:
    reader = csv.DictReader(file)
    for row in reader:
        total += float(row["Marks"])
        count += 1

print("Average:", total / count if count else 0)

import json

contacts = {
    "Ravi": "9876543210",
    "Anita": "9123456780"
}

with open("contacts.json", "w", encoding="utf-8") as file:
    json.dump(contacts, file, indent=2)

with open("contacts.json", "r", encoding="utf-8") as file:
    contacts = json.load(file)

print(contacts.get("Ravi"))

from datetime import datetime

message = input("Enter log message: ")

with open("app.log", "a", encoding="utf-8") as file:
    timestamp = datetime.now().isoformat(timespec="seconds")
    file.write(f"{timestamp} - {message}\n")

print("Log saved.")