CSV Module

Introduction

The csv module provides functionality for reading and writing CSV files.

Reading CSV

import csv

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

# With headers
with open("data.csv", "r") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row["name"], row["age"])

Writing CSV

with open("output.csv", "w", newline="") as f:
    writer = csv.writer(f)
    writer.writerow(["Name", "Age", "City"])
    writer.writerows([
        ["Alice", 30, "NYC"],
        ["Bob", 25, "LA"]
    ])

# With dictionaries
with open("output.csv", "w", newline="") as f:
    writer = csv.DictWriter(f, fieldnames=["name", "age"])
    writer.writeheader()
    writer.writerow({"name": "Alice", "age": 30})

Custom Delimiters

# Tab-separated
writer = csv.writer(f, delimiter="\t")

# Custom quoting
writer = csv.writer(f, quoting=csv.QUOTE_ALL)

Practice Problems

1. Read CSV with different delimiters
2. Convert CSV to dictionary
3. Handle missing values in CSV
4. Write nested data to CSV
5. Merge multiple CSV files