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Scrapy Spider传入参数 Scrapy中怎样向Spider传入参数的方法实现

pengjunlee 人气:0
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在使用Scrapy爬取数据时,有时会碰到需要根据传递给Spider的参数来决定爬取哪些Url或者爬取哪些页的情况。

例如,百度贴吧的放置奇兵吧的地址如下,其中 kw参数用来指定贴吧名称、pn参数用来对帖子进行翻页。

https://tieba.baidu.com/f?kw=放置奇兵&ie=utf-8&pn=250

如果我们希望通过参数传递的方式将贴吧名称和页数等参数传给Spider,来控制我们要爬取哪一个贴吧、爬取哪些页。遇到这种情况,有以下两种方法向Spider传递参数。

方式一

通过 scrapy crawl 命令的 -a 参数向 spider 传递参数。

# -*- coding: utf-8 -*-
import scrapy

class TiebaSpider(scrapy.Spider):
  name = 'tieba' # 贴吧爬虫
  allowed_domains = ['tieba.baidu.com'] # 允许爬取的范围
  start_urls = [] # 爬虫起始地址

  # 命令格式: scrapy crawl tieba -a tiebaName=放置奇兵 -a pn=250
  def __init__(self, tiebaName=None, pn=None, *args, **kwargs):
    print('< 贴吧名称 >: ' + tiebaName)
    super(eval(self.__class__.__name__), self).__init__(*args, **kwargs)
    self.start_urls = ['https://tieba.baidu.com/f?kw=%s&ie=utf-8&pn=%s' % (tiebaName,pn)]

  def parse(self, response):
    print(response.request.url) # 结果:https://tieba.baidu.com/f?kw=%E6%94%BE%E7%BD%AE%E5%A5%87%E5%85%B5&ie=utf-8&pn=250

方式二

仿照 scrapy 的 crawl 命令的源代码,重新自定义一个专用命令。

settings.py

首先,需要在settings.py文件中增加如下配置来指定自定义 scrapy 命令的存放目录。

# 指定 Scrapy 命令存放目录
COMMANDS_MODULE = 'baidu_tieba.commands'

run.py

在指定的命令存放目录中创建命令文件,在这里我们创建的命令文件为 run.py ,将来执行的命令格式为:
scrapy run [ -option option_value]

import scrapy.commands.crawl as crawl
from scrapy.exceptions import UsageError
from scrapy.commands import ScrapyCommand


class Command(crawl.Command):

  def add_options(self, parser):
    # 为命令添加选项
    ScrapyCommand.add_options(self, parser)
    parser.add_option("-k", "--keyword", type="str", dest="keyword", default="",
             help="set the tieba's name you want to crawl")
    parser.add_option("-p", "--pageNum", type="int", action="store", dest="pageNum", default=0,
             help="set the page number you want to crawl")

  def process_options(self, args, opts):
    # 处理从命令行中传入的选项参数
    ScrapyCommand.process_options(self, args, opts)
    if opts.keyword:
      tiebaName = opts.keyword.strip()
      if tiebaName != '':
        self.settings.set('TIEBA_NAME', tiebaName, priority='cmdline')
    else:
      raise UsageError("U must specify the tieba's name to crawl,use -kw TIEBA_NAME!")
    self.settings.set('PAGE_NUM', opts.pageNum, priority='cmdline')

  def run(self, args, opts):
    # 启动爬虫
    self.crawler_process.crawl('tieba')
    self.crawler_process.start()

pipelines.py

在BaiduTiebaPipeline的open_spider()方法中利用 run 命令传入的参数对TiebaSpider进行初始化,在这里示例设置了一下start_urls。

# -*- coding: utf-8 -*-
import json

class BaiduTiebaPipeline(object):

  @classmethod
  def from_settings(cls, settings):
    return cls(settings)

  def __init__(self, settings):
    self.settings = settings

  def open_spider(self, spider):
    # 开启爬虫
    spider.start_urls = [
      'https://tieba.baidu.com/f?kw=%s&ie=utf-8&pn=%s' % (self.settings['TIEBA_NAME'], self.settings['PAGE_NUM'])]

  def close_spider(self, spider):
    # 关闭爬虫
    pass

  def process_item(self, item, spider):
    # 将帖子内容保存到文件
    with open('tieba.txt', 'a', encoding='utf-8') as f:
      json.dump(dict(item), f, ensure_ascii=False, indent=2)
    return item

设置完成后,别忘了在settings.py中启用BaiduTiebaPipeline。 

ITEM_PIPELINES = {
  'baidu_tieba.pipelines.BaiduTiebaPipeline': 50,
}

启动示例

大功告成,参照如下命令格式启动贴吧爬虫。 

scrapy run -k 放置奇兵 -p 250

参考文章:

https://blog.csdn.net/c0411034/article/details/81750028 

https://blog.csdn.net/qq_24760381/article/details/80361400 

https://blog.csdn.net/qq_38282706/article/details/80991196 

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