是把对应的csv打开了，关闭之后运行就没问题，
把一个csv文件打乱顺序拆分为指定百分比的训练集和测试集，实现如下：

import csv
import os
import random


def split_csv(path, total_len, per):

    # 如果train.csv和vali.csv存在就删除
    if os.path.exists('E:/Server/U2S_fake_face_test_0909_train.csv'):
        os.remove('E:/Server/U2S_fake_face_test_0909_train.csv')
    if os.path.exists('E:/Server/U2S_fake_face_test_0909_test.csv'):
        os.remove('E:/Server/U2S_fake_face_test_0909_test.csv')

    with open(path, 'r', newline='') as file:
        csvreader = csv.reader(file)
        train_num = round(total_len * per / 100)
        index = random.sample(list(range(total_len)), train_num)
        print('index', len(index), index,)
        i = 0
        for ind in csvreader:

            if i in index:
                # train.csv存放路径
                csv_path = os.path.join("E:\\Server", 'U2S_fake_face_test_0909_train.csv')
                # print(csv_path)
                # 不存在此文件的时候，就创建
                if not os.path.exists(csv_path):
                    with open(csv_path, 'w', newline='') as file:
                        csvwriter = csv.writer(file)
                        csvwriter.writerow(ind)
                        i += 1
                        # 存在的时候就往里面添加
                else:
                    with open(csv_path, 'a', newline='') as file:
                        csvwriter = csv.writer(file)
                        csvwriter.writerow(ind)
                        i += 1
            else:
            # vali.csv存放路径
                csv_path = os.path.join("E:\\Server", 'U2S_fake_face_test_0909_test.csv')
                # print(csv_path)
                # 不存在此文件的时候，就创建
                if not os.path.exists(csv_path):
                    with open(csv_path, 'w', newline='') as file:
                        csvwriter = csv.writer(file)
                        csvwriter.writerow(ind)
                        i += 1
                else:
                    with open(csv_path, 'a', newline='') as file:
                        csvwriter = csv.writer(file)
                        csvwriter.writerow(ind)
                        i += 1

    print("训练集和验证集分离成功")
    return
if __name__ == '__main__':

    path = "E:/Server/U2S_fake_face_test_0909.csv"
    total_len = len(open(path, 'r').readlines())# csv文件行数
    per = 59# 分割比例%

    split_csv(path, total_len, per)