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"""Set User-Agent header per spider or use a default value from settings"""
from __future__ import annotations
from typing import TYPE_CHECKING
from scrapy import Request, Spider, signals
if TYPE_CHECKING:
# typing.Self requires Python 3.11
from typing_extensions import Self
from scrapy.crawler import Crawler
from scrapy.http import Response
class UserAgentMiddleware:
"""This middleware allows spiders to override the user_agent"""
def __init__(self, user_agent: str = "Scrapy"):
self.user_agent = user_agent
@classmethod
def from_crawler(cls, crawler: Crawler) -> Self:
o = cls(crawler.settings["USER_AGENT"])
crawler.signals.connect(o.spider_opened, signal=signals.spider_opened)
return o
def spider_opened(self, spider: Spider) -> None:
self.user_agent = getattr(spider, "user_agent", self.user_agent)
def process_request(
self, request: Request, spider: Spider
) -> Request | Response | None:
if self.user_agent:
request.headers.setdefault(b"User-Agent", self.user_agent)
return None
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