欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识！
您现在的位置是： 首页

Python爬虫：scrapy框架请求参数meta、headers、cookies一探究竟

程序员文章站 2022-05-11 17:28:55
...

对于scrapy请参数，会经常用到，不过没有深究

今天我就来探索下scrapy请求时所携带的3个重要参数headers, cookies, meta

原生参数

首先新建myscrapy项目，新建my_spider爬虫

通过访问：http://httpbin.org/get 来测试请求参数

将爬虫运行起来

# -*- coding: utf-8 -*-

from scrapy import Spider, Request
import logging


class MySpider(Spider):
    name = 'my_spider'
    allowed_domains = ['httpbin.org']
    start_urls = [
        'http://httpbin.org/get'
    ]

    def parse(self, response):
        self.write_to_file("*" * 40)
        self.write_to_file("response text: %s" % response.text)
        self.write_to_file("response headers: %s" % response.headers)
        self.write_to_file("response meta: %s" % response.meta)
        self.write_to_file("request headers: %s" % response.request.headers)
        self.write_to_file("request cookies: %s" % response.request.cookies)
        self.write_to_file("request meta: %s" % response.request.meta)

    def write_to_file(self, words):
        with open("logging.log", "a") as f:
            f.write(words)


if __name__ == '__main__':
    from scrapy import cmdline
    cmdline.execute("scrapy crawl my_spider".split())

保存到文件中的信息如下：

response text: 
{
    "args":{},
    "headers":{
        "Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
        "Accept-Encoding":"gzip,deflate",
        "Accept-Language":"en",
        "Connection":"close",
        "Host":"httpbin.org",
        "User-Agent":"Scrapy/1.5.1 (+https://scrapy.org)"
    },
    "origin":"223.72.90.254",
    "url":"http://httpbin.org/get"
}

response headers: 
{
    b'Server': [b'gunicorn/19.8.1'], 
    b'Date': [b'Sun, 22 Jul 2018 10:03:15 GMT'], 
    b'Content-Type': [b'application/json'], 
    b'Access-Control-Allow-Origin': [b'*'], 
    b'Access-Control-Allow-Credentials': [b'true'], 
    b'Via': [b'1.1 vegur']
}

response meta: 
{
    'download_timeout': 180.0, 
    'download_slot': 'httpbin.org', 
    'download_latency': 0.5500118732452393
}

request headers: 
{
    b'Accept': [b'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'], b'Accept-Language': [b'en'], 
    b'User-Agent': [b'Scrapy/1.5.1 (+https://scrapy.org)'], 
    b'Accept-Encoding': [b'gzip,deflate']
}

request cookies: 
{}

request meta: 
{
    'download_timeout': 180.0, 
    'download_slot': 'httpbin.org', 
    'download_latency': 0.5500118732452393
}

meta

通过上面的输出比较，发现 response 和 request 的meta参数是一样的，meta的功能就是从request携带信息，将其传递给response的

修改下代码，测试下传递效果

# -*- coding: utf-8 -*-

from scrapy import Spider, Request
import logging


class MySpider(Spider):
    name = 'my_spider'
    allowed_domains = ['httpbin.org']
    start_urls = [
        'http://httpbin.org/get'
    ]

    def start_requests(self):
        for url in self.start_urls:
            yield Request(url, meta={"uid": "this is uid of meta"})

    def parse(self, response):
        print("request meta: %s" % response.request.meta.get("uid"))
        print("response meta: %s" % response.meta.get("uid"))

输出如下

request meta: this is uid of meta
response meta: this is uid of meta

看来获取request中meta这两种方式都可行，这里的meta类似字典，可以按照字典获取key-value的形式获取对应的值
当然代理设置也是通过meta的
以下是一个代理中间件的示例

import random


class ProxyMiddleware(object):       
    def process_request(self, request, spider):
        proxy=random.choice(proxies)
        request.meta["proxy"] = proxy

headers

按照如下路径，打开scrapy的default_settings文件

from scrapy.settings import default_settings

发现是这么写的

USER_AGENT = 'Scrapy/%s (+https://scrapy.org)' % import_module('scrapy').__version__

DEFAULT_REQUEST_HEADERS = {
    'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
    'Accept-Language': 'en',
}

修改下请求头，看服务器返回的信息

# -*- coding: utf-8 -*-

from scrapy import Spider, Request
import logging


class MySpider(Spider):
    name = 'my_spider'
    allowed_domains = ['httpbin.org']
    start_urls = [
        'http://httpbin.org/get',
    ]

    def start_requests(self):
        for url in self.start_urls:
            yield Request(url, headers={"User-Agent": "Chrome"})

    def parse(self, response):
        logging.debug("*" * 40)
        logging.debug("response text: %s" % response.text)
        logging.debug("response headers: %s" % response.headers)
        logging.debug("request headers: %s" % response.request.headers)


if __name__ == '__main__':
    from scrapy import cmdline
    cmdline.execute("scrapy crawl my_spider".split())

输出如下

response text: 
{
    "args":{},
    "headers":
    {
        "Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
        "Accept-Encoding":"gzip,deflate",
        "Accept-Language":"en",
        "Connection":"close",
        "Host":"httpbin.org",
        "User-Agent":"Chrome"
    },
    "origin":"122.71.64.121",
    "url":"http://httpbin.org/get"
}

response headers: 
{
    b'Server': [b'gunicorn/19.8.1'], 
    b'Date': [b'Sun, 22 Jul 2018 10:29:26 GMT'], 
    b'Content-Type': [b'application/json'], 
    b'Access-Control-Allow-Origin': [b'*'], 
    b'Access-Control-Allow-Credentials': [b'true'], 
    b'Via': [b'1.1 vegur']
}


request headers: 
{
    b'User-Agent': [b'Chrome'], 
    b'Accept': [b'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'], b'Accept-Language': [b'en'], 
    b'Accept-Encoding': [b'gzip,deflate']
}

看到 request 和 服务器接收到并返回的的 headers（User-Agent）变化了，说明已经把默认的User-Agent修改了

看到default_settings中默认使用了中间件UserAgentMiddleware

'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': 500,

源码如下


class UserAgentMiddleware(object):
    """This middleware allows spiders to override the user_agent"""

    def __init__(self, user_agent='Scrapy'):
        self.user_agent = user_agent

    @classmethod
    def from_crawler(cls, crawler):
        o = cls(crawler.settings['USER_AGENT'])
        crawler.signals.connect(o.spider_opened, signal=signals.spider_opened)
        return o

    def spider_opened(self, spider):
        self.user_agent = getattr(spider, 'user_agent', self.user_agent)

    def process_request(self, request, spider):
        if self.user_agent:
            request.headers.setdefault(b'User-Agent', self.user_agent)

仔细阅读源码，发现无非就是对User-Agent读取和设置操作，仿照源码写自己的中间件

这里使用fake_useragent库来随机获取请求头，详情可参看：
https://blog.csdn.net/mouday/article/details/80476409

middlewares.py 编写自己的中间件

from fake_useragent import UserAgent


class UserAgentMiddleware(object):
    def process_request(self, request, spider):
        ua = UserAgent()
        user_agent = ua.chrome
        request.headers.setdefault(b'User-Agent', user_agent)

settings.py 用自己的中间件替换默认中间件

DOWNLOADER_MIDDLEWARES = {
    'scrapy.downloadermiddlewares.useragent.UserAgentMiddleware': None,
    'myscrapy.middlewares.UserAgentMiddleware': 500
}

输出如下：

request headers: 
{
    b'Accept': [b'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'], b'Accept-Language': [b'en'], 
    b'User-Agent': [b'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.93 Safari/537.36'], 
    b'Accept-Encoding': [b'gzip,deflate']
}

关于scrapy请求头设置，可以参考我之前的文章：
https://blog.csdn.net/mouday/article/details/80776030

cookies

上面的信息中少了个response.cookies，如果添加上回报错：

AttributeError: 'TextResponse' object has no attribute 'cookies'

说明响应是不带cookies参数的

通过 http://httpbin.org/cookies 测试cookies

# -*- coding: utf-8 -*-

from scrapy import Spider, Request
import logging


class MySpider(Spider):
    name = 'my_spider'
    allowed_domains = ['httpbin.org']
    start_urls = [
        'http://httpbin.org/cookies'
    ]


    def start_requests(self):
        for url in self.start_urls:
            yield Request(url, cookies={"username": "pengshiyu"})

    def parse(self, response):
        logging.debug("*" * 40)
        logging.debug("response text: %s" % response.text)
        logging.debug("request headers: %s" % response.request.headers)
        logging.debug("request cookies: %s" % response.request.cookies)


if __name__ == '__main__':
    from scrapy import cmdline
    cmdline.execute("scrapy crawl my_spider".split())

返回值如下：

response text: 
{
    "cookies":
        {
        "username":"pengshiyu"
        }
}

request headers: 
{
    b'Accept': [b'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'], b'Accept-Language': [b'en'], 
    b'User-Agent': [b'Scrapy/1.5.1 (+https://scrapy.org)'], 
    b'Accept-Encoding': [b'gzip,deflate'], 
    b'Cookie': [b'username=pengshiyu']
}

request cookies: 
{
    'username': 'pengshiyu'
}

服务器端已经接收到我的cookie值了，不过request的headers也包含了相同的cookie，保存到了键为Cookie下面

其实并没有什么cookie，浏览器请求的·cookies·被包装到了·headers·中发送给服务器端
既然这样，在headers中包含Cookie试试

 def start_requests(self):
        for url in self.start_urls:
            yield Request(url, headers={"Cookie": {"username": "pengshiyu"}})

返回结果

response text: 
{
    "cookies":{}
}

request headers: 
{
    b'Accept': [b'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'], b'Accept-Language': [b'en'], 
    b'User-Agent': [b'Scrapy/1.5.1 (+https://scrapy.org)'], 
    b'Accept-Encoding': [b'gzip,deflate']
}


request cookies: 
{}

cookies 是空的，设置失败

我们找到 default_settings 中的cookie中间件

'scrapy.downloadermiddlewares.cookies.CookiesMiddleware': 700

class CookiesMiddleware(object):
    """This middleware enables working with sites that need cookies"""

    def __init__(self, debug=False):
        self.jars = defaultdict(CookieJar)
        self.debug = debug

    @classmethod
    def from_crawler(cls, crawler):
        if not crawler.settings.getbool('COOKIES_ENABLED'):
            raise NotConfigured
        return cls(crawler.settings.getbool('COOKIES_DEBUG'))

    def process_request(self, request, spider):
        if request.meta.get('dont_merge_cookies', False):
            return

        cookiejarkey = request.meta.get("cookiejar")
        jar = self.jars[cookiejarkey]
        cookies = self._get_request_cookies(jar, request)
        for cookie in cookies:
            jar.set_cookie_if_ok(cookie, request)

        # set Cookie header
        request.headers.pop('Cookie', None)
        jar.add_cookie_header(request)
        self._debug_cookie(request, spider)

    def process_response(self, request, response, spider):
        if request.meta.get('dont_merge_cookies', False):
            return response

        # extract cookies from Set-Cookie and drop invalid/expired cookies
        cookiejarkey = request.meta.get("cookiejar")
        jar = self.jars[cookiejarkey]
        jar.extract_cookies(response, request)
        self._debug_set_cookie(response, spider)

        return response

    def _debug_cookie(self, request, spider):
        if self.debug:
            cl = [to_native_str(c, errors='replace')
                  for c in request.headers.getlist('Cookie')]
            if cl:
                cookies = "\n".join("Cookie: {}\n".format(c) for c in cl)
                msg = "Sending cookies to: {}\n{}".format(request, cookies)
                logger.debug(msg, extra={'spider': spider})

    def _debug_set_cookie(self, response, spider):
        if self.debug:
            cl = [to_native_str(c, errors='replace')
                  for c in response.headers.getlist('Set-Cookie')]
            if cl:
                cookies = "\n".join("Set-Cookie: {}\n".format(c) for c in cl)
                msg = "Received cookies from: {}\n{}".format(response, cookies)
                logger.debug(msg, extra={'spider': spider})

    def _format_cookie(self, cookie):
        # build cookie string
        cookie_str = '%s=%s' % (cookie['name'], cookie['value'])

        if cookie.get('path', None):
            cookie_str += '; Path=%s' % cookie['path']
        if cookie.get('domain', None):
            cookie_str += '; Domain=%s' % cookie['domain']

        return cookie_str

    def _get_request_cookies(self, jar, request):
        if isinstance(request.cookies, dict):
            cookie_list = [{'name': k, 'value': v} for k, v in \
                    six.iteritems(request.cookies)]
        else:
            cookie_list = request.cookies

        cookies = [self._format_cookie(x) for x in cookie_list]
        headers = {'Set-Cookie': cookies}
        response = Response(request.url, headers=headers)

        return jar.make_cookies(response, request)

观察源码，发现以下几个方法

# process_request
jar.add_cookie_header(request)   # 添加cookie到headers

# process_response
jar.extract_cookies(response, request)  # 提取出cookie

# _debug_cookie 
request.headers.getlist('Cookie')  # 从headers获取cookie

# _debug_set_cookie
response.headers.getlist('Set-Cookie')  # 从headers获取Set-Cookie

几个参数：

# settings
COOKIES_ENABLED
COOKIES_DEBUG

# meta
dont_merge_cookies
cookiejar

# headers
Cookie
Set-Cookie

使用最开始cookie部分的代码，为了看的清晰，我删除了headers中其他参数，下面逐个做测试

1、COOKIES_ENABLED

COOKIES_ENABLED = True (默认)

response text: 
{
    "cookies":{"username":"pengshiyu"}
}

request headers: 
{
    b'Cookie': [b'username=pengshiyu']
}

request cookies: 
{
    'username': 'pengshiyu'
}

一切ok
COOKIES_ENABLED = False 

response text: 
{
    "cookies":{}
}

request headers: 
{}

request cookies: 
{
    'username': 'pengshiyu'
}

虽然request的cookies有内容，不过headers没有加进去，所以服务器端没有获取到cookie

注意：查看请求的真正cookie，应该在request的header中查看

2、COOKIES_DEBUG
COOKIES_DEBUG = False (默认)

DEBUG: Crawled (200) <GET http://httpbin.org/cookies> (referer: None)

COOKIES_DEBUG = True
多输出了下面一句，可以看到我设置的cookie

[scrapy.downloadermiddlewares.cookies] DEBUG: Sending cookies to: <GET http://httpbin.org/cookies>
Cookie: username=pengshiyu

当然，debug模式下服务器肯定能正常接收我的cookie

3、dont_merge_cookies
设置meta={"dont_merge_cookies": True} 默认为 False

response text: 
{
    "cookies":{}
}

request headers: 
{}

request cookies: 
{
    'username': 'pengshiyu'
}

服务器并没有接收到我的cookie

4、cookiejar
直接通过response.request.meta.get("cookiejar")获取


response text: 
{"cookies":{"username":"pengshiyu"}}

request headers: 
{b'Cookie': [b'username=pengshiyu']}

request cookies: 
{'username': 'pengshiyu'}

request cookiejar: 
None

啥也没有

5、Cookie
直接获取：response.request.headers.get("Cookie"))

headers Cookie: 
b'username=pengshiyu'

看来这里已经被处理成字节串了

修改Request请求参数
cookies={"username": "pengshiyu", "password": "123456"}

# response.request.headers.get("Cookie"))
headers Cookie: 
b'username=pengshiyu; password=123456'

# request.headers.getlist('Cookie')
headers Cookies: 
[b'username=pengshiyu; password=123456']

很明显，两个获取方式，一个获取的是字符串，一个获取的是列表

6、Set-Cookie

同样，我通过以下

response.headers.get("Set-Cookie")
response.headers.getlist("Set-Cookie")

还是啥都没有

headers Set-Cookie: None
headers Set-Cookies: []

不过，到目前为止，cookie设置的大概流程应该如下：

request cookies: {'username': 'pengshiyu', 'password': '123456'}
request cookiejar: None
request Cookie: b'username=pengshiyu; password=123456'
response text: {"cookies":{"password":"123456","username":"pengshiyu"}}
response Set-Cookie: None
response Set-Cookies: []

7、接收服务器传递过来的cookie

将请求链接改为 ：’http://httpbin.org/cookies/set/key/value’
开启 COOKIES_DEBUG
在debug中看到如下变化

Sending cookies to: <GET http://httpbin.org/cookies/set/key/value>
Cookie: username=pengshiyu; password=123456

Received cookies from: <302 http://httpbin.org/cookies/set/key/value>
Set-Cookie: key=value; Path=/

Redirecting (302) to <GET http://httpbin.org/cookies> from <GET http://httpbin.org/cookies/set/key/value>

Sending cookies to: <GET http://httpbin.org/cookies>
Cookie: key=value; username=pengshiyu; password=123456

日志看出他进行了两次请求，看到中间的cookie变化：

发送 -> 接收 -> 发送

第二次发送的cookie包含了第一次请求时服务器端传递过来的cookie，说明scrapy对服务器端和客户端的cookie进行了管理

最后的cookie输出

request cookies: {'username': 'pengshiyu', 'password': '123456'}
request cookiejar: None
request Cookie: b'key=value; username=pengshiyu; password=123456'
response text: {"cookies":{"key":"value","password":"123456","username":"pengshiyu"}}
response Set-Cookie: None

request的cookies并没有变化，而request.headers.get(“Cookie”)已经发生了变化

8、接收服务器传递过来的 同key键cookie
将请求链接换为：httpbin.org/cookies/set/username/pengpeng

Sending cookies to: <GET http://httpbin.org/cookies/set/username/pengpeng>
Cookie: username=pengshiyu

Received cookies from: <302 http://httpbin.org/cookies/set/username/pengpeng>
Set-Cookie: username=pengpeng; Path=/

Redirecting (302) to <GET http://httpbin.org/cookies> from <GET http://httpbin.org/cookies/set/username/pengpeng>

Sending cookies to: <GET http://httpbin.org/cookies>
Cookie: username=pengshiyu

发现虽然收到了username=pengpeng但是，第二次发请求的时候，又发送了原来的的cookieusername=pengshiyu

这说明客户端设置的cookie优先级高于服务器端传递过来的cookie

9、取消使用中间件CookiesMiddleware

DOWNLOADER_MIDDLEWARES = {
    'scrapy.downloadermiddlewares.cookies.CookiesMiddleware': None
}

请求链接：http://httpbin.org/cookies

request cookies: {'username': 'pengshiyu'}
request cookiejar: None
request Cookie: None
response text: {"cookies":{}}
response Set-Cookie: None
response Set-Cookies: []

这个效果类似COOKIES_ENABLED = False

10、自定义cookie池

class RandomCookiesMiddleware(object):
    def process_request(self, request, spider):
        cookies = []
        cookie = random.choice(cookies)
        request.cookies = cookie

同样需要设置

DOWNLOADER_MIDDLEWARES = {
    'myscrapy.middlewares.RandomCookiesMiddleware': 600
}

注意到scrapy的中间件CookiesMiddleware值是700,为了cookie设置生效，需要在这个中间件启用之前就设置好自定义的cookie，优先级按照从小到大的顺序执行，所以我们自己自定义的cookie中间件需要小于 < 700

'scrapy.downloadermiddlewares.cookies.CookiesMiddleware': 700,

总结

参数 设置 获取 说明
meta Request(url, meta={“uid”: “100”}) request.meta[“uid”] = “100” response.request.meta.get(“uid”) response.meta.get(“uid”) 携带request参数给response,或设置代理
headers Request(url, headers={“User-Agent”: “chrome”}) request.headers[“User-Agent”]=”chrome” USER_AGENT=”chrome” response.request.headers.get(“User-Agent”) 设置客户端请求头参数
cookies Request(url, cookies={“username”: “pengshiyu”} ) request.cookies = {“username”: “pengshiyu”} response.request.cookies response.request.headers.get(“Cookie”) response.headers.get(‘Set-Cookie’) 客户端请求头中的Cookie参数，管理客户端与服务器端之间的会话识别

常用的中间件如下

import random
from fake_useragent import UserAgent


class RandomUserAgentMiddleware(object):
    def process_request(self, request, spider):
        ua = UserAgent()
        user_agent = ua.chrome
        request.headers.setdefault(b'User-Agent', user_agent)


class RandomProxyMiddleware(object):
    def process_request(self, request, spider):
        proxies = []
        proxy = random.choice(proxies)
        request.meta["proxy"] = proxy


class RandomCookiesMiddleware(object):
    def process_request(self, request, spider):
        cookies = []
        cookie = random.choice(cookies)
        request.cookies = cookie

当然，cookies 和 proxies 需要结合自己的情况补全

上一篇： Linux使用Samba共享文件

下一篇： [Ubuntu 16.04] [Memos] install samba

推荐阅读