编写一段代码：python爬取豆瓣电影top250中的电影名,编剧，主演,电影类型并保存在csv文件中,要有反反爬机制，注意缩进格式

好的，以下是可以回答的代码：

import requests
from lxml import etree
import csv
import time
from random import randint

def get_html(url):
    headers = {
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.3"}
    try:
        response = requests.get(url, headers=headers)
        if response.status_code == 200:
            return response.text
    except requests.RequestException:
        return None

def parse_html(html):
    selectors = etree.HTML(html)
    items = selectors.xpath('//ol[@class="grid_view"]/li')
    for item in items:
        title = item.xpath('.//span[@class="title"]/text()')[0]
        scriptwriter = item.xpath('.//p[@class=""]/text()')[0].strip().split('\n')[0][5:]
        actors = item.xpath('.//p[@class=""]/text()')[0].strip().split('\n')[1][3:]
        genres = item.xpath('.//p[@class=""]/text()')[1].strip().split('\n')[1:]
        genre = '/'.join(genres)
        yield {
            'title': title,
            'scriptwriter': scriptwriter,
            'actors': actors,
            'genre': genre
        }

def save_csv(data):
    with open('豆瓣电影top250.csv', 'w', encoding='utf-8', newline='') as csvfile:
        fieldnames = ['title', 'scriptwriter', 'actors', 'genre']
        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
        writer.writeheader()
        for item in data:
            writer.writerow(item)

if __name__ == '__main__':
    urls = ['https://movie.douban.com/top250?start={}'.format(i) for i in range(0, 250, 25)]
    data = []
    for url in urls:
        html = get_html(url)
        items = parse_html(html)
        data.extend(items)
        time.sleep(randint(3, 5))
    save_csv(data)

这是一个简单的爬虫代码，用于爬取豆瓣电影top250的电影名、编剧、主演、电影类型，并将结果保存在csv文件中。其中也包括了反爬虫机制，使用了随机的时间间隔，用以减少对豆瓣网站的请求次数，避免被封禁。