csv行的开头和结尾有多余的逗号，如何删除？

import csv

def remove_extra_commas(csv_file):
    with open(csv_file, 'r') as file:
        reader = csv.reader(file)
        rows = [row for row in reader]

    modified_rows = []
    for row in rows:
        if row and row[0] == '':
            row = row[1:]
        if row and row[-1] == '':
            row = row[:-1]
        modified_rows.append(row)

    with open(csv_file, 'w', newline='') as file:
        writer = csv.writer(file)
        writer.writerows(modified_rows)

# 调用示例
remove_extra_commas('example.csv')