如果問題很單純，甚至連 csv 都可以不使用:

with open('old.csv') as reader, open('new.csv', 'w') as writer:
    for line in reader:
        items = line.strip().split()
        print(' '.join(items[:2]+items[3:]), file=writer)

寫個 general 的:

import csv

def del_cvs_col(fname, newfname, idxs, delimiter=' '):
    with open(fname) as csvin, open(newfname, 'w') as csvout:
        reader = csv.reader(csvin, delimiter=delimiter)
        writer = csv.writer(csvout, delimiter=delimiter)
        rows = (tuple(item for idx, item in enumerate(row) if idx not in idxs) for row in reader)
        writer.writerows(rows)

del_cvs_col('a.csv', 'b.csv', [2])

del_cvs_col 會將 fname 轉成 newfname 用 delimiter 來做分割字元，且會去除掉在 idxs中指定的列。

我回答過的問題: Python-QA