Working with CSV Data

import csv
import io

# Write CSV (using StringIO for demo)
output = io.StringIO()
writer = csv.writer(output)
writer.writerow(["Name", "Age", "City"])
writer.writerow(["Alice", 25, "Mumbai"])
writer.writerow(["Bob", 30, "Delhi"])
writer.writerow(["Charlie", 28, "Bangalore"])

csv_content = output.getvalue()
print("=== CSV Output ===")
print(csv_content)

# Read CSV
input_data = io.StringIO(csv_content)
reader = csv.reader(input_data)
header = next(reader)
print(f"Columns: {header}")
for row in reader:
    print(f"  {row[0]}, age {row[1]}, from {row[2]}")

# DictReader — access by column name
input_data2 = io.StringIO(csv_content)
dict_reader = csv.DictReader(input_data2)
print("\n=== DictReader ===")
for row in dict_reader:
    print(f"  {row['Name']} lives in {row['City']}")

# Practical: data analysis
input_data3 = io.StringIO(csv_content)
ages = []
for row in csv.DictReader(input_data3):
    ages.append(int(row['Age']))
print(f"\nAvg age: {sum(ages)/len(ages):.1f}")