Working with CSV Files

CSV (comma-separated values) is the format spreadsheets and many tools speak. The standard-library csv module handles the tricky details like quoting for you, so you almost never split on commas by hand.

To write rows, wrap the file in a csv.writer and call writerow():

import csv

rows = [["name", "score"], ["Ada", 90], ["Sam", 75]]
with open("scores.csv", "w", newline="") as f:
    writer = csv.writer(f)
    for row in rows:
        writer.writerow(row)

The newline="" argument prevents blank lines between rows on some systems. Always include it when writing CSV.

To read rows back as dictionaries keyed by the header, use csv.DictReader. It reads the first line as the header automatically:

with open("scores.csv", "r", newline="") as f:
    reader = csv.DictReader(f)
    for row in reader:
        print(row["name"], row["score"])

Each row is a dict like {"name": "Ada", "score": "90"}. Note the values come back as strings, so convert with int(row["score"]) when you need a number.