ফাইল I/O (File I/O)

# Writing a file
with open("grocery_list.txt", "w") as f:
    f.write("Apples\n")
    f.write("Bread\n")
    f.write("Milk\n")
    f.write("Cheese\n")
print("File written!")

# Reading the entire file
with open("grocery_list.txt", "r") as f:
    content = f.read()
print("Full content:")
print(content)

# Reading line by line (memory efficient for big files)
with open("grocery_list.txt", "r") as f:
    for line_number, line in enumerate(f, start=1):
        print(f"{line_number}: {line.strip()}")

File written!
Full content:
Apples
Bread
Milk
Cheese

1: Apples
2: Bread
3: Milk
4: Cheese

# Append to an existing file
with open("grocery_list.txt", "a") as f:
    f.write("Eggs\n")
    f.write("Butter\n")

# Read all lines into a list
with open("grocery_list.txt", "r") as f:
    lines = f.readlines()

print("Raw lines:", lines[:3])  # First 3 (notice the \n)

# Clean up — strip whitespace from each line
clean_lines = [line.strip() for line in lines]
print("Clean lines:", clean_lines)
print(f"Total items: {len(clean_lines)}")

Raw lines: ['Apples\n', 'Bread\n', 'Milk\n']
Clean lines: ['Apples', 'Bread', 'Milk', 'Cheese', 'Eggs', 'Butter']
Total items: 6

import csv

# Writing a CSV file
students = [
    ["Name", "Grade", "Score"],
    ["Anika", "A", "95"],
    ["Rafi", "B", "87"],
    ["Sadia", "A", "92"],
]

with open("students.csv", "w", newline="") as f:
    writer = csv.writer(f)
    writer.writerows(students)
print("CSV written!")

# Reading a CSV file
with open("students.csv", "r") as f:
    reader = csv.reader(f)
    header = next(reader)       # Skip the header row
    print(f"Columns: {header}")
    for row in reader:
        print(f"{row[0]} scored {row[2]} (Grade {row[1]})")

print()

# Using DictReader for named columns
with open("students.csv", "r") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(f"{row['Name']}: {row['Score']}")

CSV written!
Columns: ['Name', 'Grade', 'Score']
Alice scored 95 (Grade A)
Bob scored 87 (Grade B)
Charlie scored 92 (Grade A)

Alice: 95
Bob: 87
Charlie: 92