Python で CSV ファイルの読み書き

read_csv.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-

import csv

with open("sample.csv", "r") as f:
    reader = csv.reader(f)
    header = next(reader)  # ヘッダを読み飛ばす
    for row in reader:     # 1 行ずつ文字列のリストとして読み込む
        print(",".join(row))

write_csv.py

#! /usr/bin/env python
# -*- coding: utf-8 -*-

import csv

header = ["A", "B", "C"]
lines = [[r * 3 + c for c in range(3)] for r in range(3)]

with open("sample.csv", "w") as f:
    writer = csv.writer(f)
    writer.writerow(header)  # 1 行ずつ出力
    writer.writerows(lines)  # 複数行をまとめて出力