将项目写入MongoDB¶在这个示例中,我们将向 MongoDB 使用 pymongo. 在Scrapy设置中指定MongoDB地址和数据库名称;MongoDB集合以item类命名。 这个例子的要点是演示如何使用 import pymongo
from itemadapter import ItemAdapter
class MongoPipeline:
collection_name = 'scrapy_items'
def __init__(self, mongo_uri, mongo_db):
self.mongo_uri = mongo_uri
self.mongo_db = mongo_db
@classmethod
def from_crawler(cls, crawler):
return cls(
mongo_uri=crawler.settings.get('MONGO_URI'),
mongo_db=crawler.settings.get('MONGO_DATABASE', 'items')
)
def open_spider(self, spider):
self.client = pymongo.MongoClient(self.mongo_uri)
self.db = self.client[self.mongo_db]
def close_spider(self, spider):
self.client.close()
def process_item(self, item, spider):
self.db[self.collection_name].insert_one(ItemAdapter(item).asdict())
return item
项目截图¶这个例子演示了如何使用 coroutine syntax 在 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
from scrapy.utils.defer import maybe_deferred_to_future
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 maybe_deferred_to_future(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 |
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