Scrapy框架学习---Request/Response(七)
Request
Request 部分源码：
# 部分代码
class Request(object_ref):
def __init__(self, url, callback=None, method='GET', headers=None, body=None,
cookies=None, meta=None, encoding='utf-8', priority=0,
dont_filter=False, errback=None):
self._encoding = encoding # this one has to be set first
self.method = str(method).upper()
self._set_url(url)
self._set_body(body)
assert isinstance(priority, int), "Request priority not an integer: %r" % priority
self.priority = priority
assert callback or not errback, "Cannot use errback without a callback"
self.callback = callback
self.errback = errback
self.cookies = cookies or {}
self.headers = Headers(headers or {}, encoding=encoding)
self.dont_filter = dont_filter
self._meta = dict(meta) if meta else None
@property
def meta(self):
if self._meta is None:
self._meta = {}
return self._meta
其中，比较常用的参数：
url: 就是需要请求，并进行下一步处理的url
callback: 指定该请求返回的Response，由那个函数来处理。
method: 请求一般不需要指定，默认GET方法，可设置为"GET", "POST", "PUT"等，且保证字符串大写
headers: 请求时，包含的头文件。一般不需要。内容一般如下：
# 自己写过爬虫的肯定知道
Host: media.readthedocs.org
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:33.0) Gecko/20100101 Firefox/33.0
Accept: text/css,/;q=0.1
Accept-Language: zh-cn,zh;q=0.8,en-us;q=0.5,en;q=0.3
Accept-Encoding: gzip, deflate
Referer: http://scrapy-chs.readthedocs.org/zh_CN/0.24/
Cookie: _ga=GA1.2.1612165614.1415584110;
Connection: keep-alive
If-Modified-Since: Mon, 25 Aug 2014 21:59:35 GMT
Cache-Control: max-age=0
meta: 比较常用，在不同的请求之间传递数据使用的。字典dict型
request_with_cookies = Request( url="http://www.example.com", cookies={'currency': 'USD', 'country': 'UY'}, meta={'dont_merge_cookies': True} )encoding: 使用默认的 'utf-8' 就行。
dont_filter: 表明该请求不由调度器过滤。这是当你想使用多次执行相同的请求,忽略重复的过滤器。默认为False。
errback: 指定错误处理函数
Response
Response部分源码：
# 部分代码
class Response(object_ref):
def __init__(self, url, status=200, headers=None, body='', flags=None, request=None):
self.headers = Headers(headers or {})
self.status = int(status)
self._set_body(body)
self._set_url(url)
self.request = request
self.flags = [] if flags is None else list(flags)
@property
def meta(self):
try:
return self.request.meta
except AttributeError:
raise AttributeError("Response.meta not available, this response " \
"is not tied to any request")
大部分参数和上面的差不多：
status: 响应码
_set_body(body)： 响应体
_set_url(url)：响应url
self.request = request
发送POST请求
-
可以使用 yield scrapy.FormRequest(url, formdata, callback)方法发送POST请求。
-
如果希望程序执行一开始就发送POST请求，可以重写Spider类的start_requests(self) 方法，并且不再调用start_urls里的url。
class mySpider(scrapy.Spider):
# start_urls = ["http://www.example.com/"]
def start_requests(self):
url = 'http://www.renren.com/PLogin.do'
# FormRequest 是Scrapy发送POST请求的方法
yield scrapy.FormRequest(
url = url,
formdata = {"email" : "smartliu_it@163.com", "password" : "axxxxxxxe"},
callback = self.parse_page
)
def parse_page(self, response):
# do something
模拟登陆
使用FormRequest.from_response()方法模拟用户登录
通常网站通过 实现对某些表单字段（如数据或是登录界面中的认证令牌等）的预填充。
使用Scrapy抓取网页时，如果想要预填充或重写像用户名、用户密码这些表单字段， 可以使用 FormRequest.from_response() 方法实现。
下面是使用这种方法的爬虫例子:
import scrapy
class LoginSpider(scrapy.Spider):
name = 'example.com'
start_urls = ['http://www.example.com/users/login.php']
def parse(self, response):
return scrapy.FormRequest.from_response(
response,
formdata={'username': 'kongshan', 'password': 'cool'},
callback=self.after_login
)
def after_login(self, response):
# check login succeed before going on
if "authentication failed" in response.body:
self.log("Login failed", level=log.ERROR)
return
# continue scraping with authenticated session...
豆瓣爬虫案例参考：
Item类设置
import scrapy
class DoubanItem(scrapy.Item):
# 用户名
user_name = scrapy.Field()
# 发布时间
publishtime = scrapy.Field()
douban.py爬虫代码
# -*- coding: utf-8 -*-
import scrapy
import urllib.request
from PIL import Image
from douBan.items import DoubanItem
class DoubanSpider(scrapy.Spider):
name = 'douban'
allowed_domains = ['douban.com']
start_urls = ['https://accounts.douban.com/login']
login_url = "https://accounts.douban.com/login"
base_url = "https://www.douban.com/"
def parse(self, response):
img_link = response.xpath('//img[@id="captcha_image"]/@src').extract_first()
captcha_id = response.xpath('//input[@name="captcha-id"]/@value').extract_first()
if img_link is None:
print("登陆时没有遇到验证码...")
formdata = {
"source": "index_nav",
"form_email": "smartliu_it@163.com",
"form_password": "kongshan123.0",
}
else:
print("登陆时遇到验证码...")
img_path = "/home/python/Desktop/douBan-豆瓣登录/douBan/spiders/douban.jpg"
urllib.request.urlretrieve(img_link, img_path)
try:
im = Image.open(img_path)
im.show()
except:
print("打开图片失败...")
captcha_solution = input("请输入验证码:")
formdata = {
"source": "index_nav",
"redir": "https://www.douban.com",
"form_email": "smartliu_it@163.com",
"form_password": "kongshan123.0",
"captcha-solution": captcha_solution,
"captcha-id": captcha_id,
"login": "登录",
}
print("正在登陆中...")
return scrapy.FormRequest(self.login_url, formdata=formdata, callback=self.login_after)
def login_after(self, response):
item = DoubanItem()
next_url = response.xpath('//span[@class="next"]/a/@href').extract_first()
title_list = response.xpath('//a[@class="lnk-people"]/text()').extract()
publish_time_list = response.xpath('//span[@class="created_at"]/@title').extract()
for title, publish_time in zip(title_list, publish_time_list):
item['user_name'] = title
item['publishtime'] = publish_time
yield item
# 拼接下一页链接
next_page = self.base_url + next_url
yield scrapy.Request(url=next_page, callback=self.login_after)
pipelines.py管道代码
import json
class DoubanPipeline(object):
# 打开爬虫时调用
def open_spider(self, spider):
self.file = open("douban.json", "w")
# 必须实现的方法
def process_item(self, item, spider):
content = json.dumps(dict(item), ensure_ascii=False) + "\n"
self.file.write(content)
return item
# 爬虫程序关闭时调用
def close_spider(self, spider):
self.file.close()
settings.py设置代码
# 请求头部
USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3192.0 Safari/537.36'
#设置下载间隔为250ms
DOWNLOAD_DELAY = 0.25
# 打开cookis传递
COOKIES_ENABLED = True
# 注册管道
ITEM_PIPELINES = {
'douBan.pipelines.DoubanPipeline': 300,
}
最后执行爬虫文件:
scrapy crawl douban
