这个例子演示了如何使用 coroutine syntax 在 ​process_item()​ 方法。

此项管道向本地运行的实例发出请求 Splash 呈现项目URL的屏幕截图。下载请求响应后，项目管道将屏幕截图保存到文件中，并将文件名添加到项目中。

import hashlib
from urllib.parse import quote

import scrapy
from itemadapter import ItemAdapter

class ScreenshotPipeline:
    """Pipeline that uses Splash to render screenshot of
    every Scrapy item."""

    SPLASH_URL = "http://localhost:8050/render.png?url={}"

    async def process_item(self, item, spider):
        adapter = ItemAdapter(item)
        encoded_item_url = quote(adapter["url"])
        screenshot_url = self.SPLASH_URL.format(encoded_item_url)
        request = scrapy.Request(screenshot_url)
        response = await spider.crawler.engine.download(request, spider)

        if response.status != 200:
            # Error happened, return item.
            return item

        # Save screenshot to file, filename will be hash of url.
        url = adapter["url"]
        url_hash = hashlib.md5(url.encode("utf8")).hexdigest()
        filename = f"{url_hash}.png"
        with open(filename, "wb") as f:
            f.write(response.body)

        # Store filename in item.
        adapter["screenshot_filename"] = filename
        return item