試想一下，前面做的實驗和例子都只有一個spider。然而，現實的開發的爬蟲肯定不止一個。既然這樣，那么就會有如下幾個問題：1、在同一個項目中怎么創建多個爬蟲的呢？2、多個爬蟲的時候是怎么將他們運行起來呢？
說明：本文章是基於前面幾篇文章和實驗的基礎上完成的。如果您錯過了，或者有疑惑的地方可以在此查看：
scrapy爬蟲成長日記之創建工程-抽取數據-保存為json格式的數據
一、創建spider
1、創建多個spider，scrapy genspider spidername domain
scrapy genspider CnblogsHomeSpider cnblogs.com
通過上述命令創建了一個spider name為CnblogsHomeSpider的爬蟲，start_urls為http://www.cnblogs.com/的爬蟲
2、查看項目下有幾個爬蟲scrapy list
[root@bogon cnblogs]# scrapy list CnblogsHomeSpider CnblogsSpider
由此可以知道我的項目下有兩個spider，一個名稱叫CnblogsHomeSpider，另一個叫CnblogsSpider。
更多關於scrapy命令可參考：http://doc.scrapy.org/en/latest/topics/commands.html
二、讓幾個spider同時運行起來
現在我們的項目有兩個spider，那么現在我們怎樣才能讓兩個spider同時運行起來呢？你可能會說寫個shell腳本一個個調用，也可能會說寫個python腳本一個個運行等。然而我在stackoverflow.com上看到。的確也有不上前輩是這么實現。然而官方文檔是這么介紹的。
1、Run Scrapy from a script
import scrapy from scrapy.crawler import CrawlerProcess class MySpider(scrapy.Spider): # Your spider definition ... process = CrawlerProcess({ 'USER_AGENT': 'Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)' }) process.crawl(MySpider) process.start() # the script will block here until the crawling is finished
這里主要通過scrapy.crawler.CrawlerProcess來實現在腳本里運行一個spider。更多的例子可以在此查看：https://github.com/scrapinghub/testspiders
2、Running multiple spiders in the same process
- 通過CrawlerProcess
import scrapy from scrapy.crawler import CrawlerProcess class MySpider1(scrapy.Spider): # Your first spider definition ... class MySpider2(scrapy.Spider): # Your second spider definition ... process = CrawlerProcess() process.crawl(MySpider1) process.crawl(MySpider2) process.start() # the script will block here until all crawling jobs are finished
- 通過CrawlerRunner
import scrapy from twisted.internet import reactor from scrapy.crawler import CrawlerRunner from scrapy.utils.log import configure_logging class MySpider1(scrapy.Spider): # Your first spider definition ... class MySpider2(scrapy.Spider): # Your second spider definition ... configure_logging() runner = CrawlerRunner() runner.crawl(MySpider1) runner.crawl(MySpider2) d = runner.join() d.addBoth(lambda _: reactor.stop()) reactor.run() # the script will block here until all crawling jobs are finished
- 通過CrawlerRunner和鏈接(chaining) deferred來線性運行
from twisted.internet import reactor, defer from scrapy.crawler import CrawlerRunner from scrapy.utils.log import configure_logging class MySpider1(scrapy.Spider): # Your first spider definition ... class MySpider2(scrapy.Spider): # Your second spider definition ... configure_logging() runner = CrawlerRunner() @defer.inlineCallbacks def crawl(): yield runner.crawl(MySpider1) yield runner.crawl(MySpider2) reactor.stop() crawl() reactor.run() # the script will block here until the last crawl call is finished
這是官方文檔提供的幾種在script里面運行spider的方法。
三、通過自定義scrapy命令的方式來運行
1、創建commands目錄
mkdir commands
注意：commands和spiders目錄是同級的
2、在commands下面添加一個文件crawlall.py
這里主要通過修改scrapy的crawl命令來完成同時執行spider的效果。crawl的源碼可以在此查看：https://github.com/scrapy/scrapy/blob/master/scrapy/commands/crawl.py
from scrapy.commands import ScrapyCommand from scrapy.crawler import CrawlerRunner from scrapy.utils.conf import arglist_to_dict class Command(ScrapyCommand): requires_project = True def syntax(self): return '[options]' def short_desc(self): return 'Runs all of the spiders' def add_options(self, parser): ScrapyCommand.add_options(self, parser) parser.add_option("-a", dest="spargs", action="append", default=[], metavar="NAME=VALUE", help="set spider argument (may be repeated)") parser.add_option("-o", "--output", metavar="FILE", help="dump scraped items into FILE (use - for stdout)") parser.add_option("-t", "--output-format", metavar="FORMAT", help="format to use for dumping items with -o") def process_options(self, args, opts): ScrapyCommand.process_options(self, args, opts) try: opts.spargs = arglist_to_dict(opts.spargs) except ValueError: raise UsageError("Invalid -a value, use -a NAME=VALUE", print_help=False) def run(self, args, opts): #settings = get_project_settings() spider_loader = self.crawler_process.spider_loader for spidername in args or spider_loader.list(): print "*********cralall spidername************" + spidername self.crawler_process.crawl(spidername, **opts.spargs) self.crawler_process.start()
這里主要是用了self.crawler_process.spider_loader.list()方法獲取項目下所有的spider，然后利用self.crawler_process.crawl運行spider
3、commands命令下添加__init__.py文件
touch __init__.py
注意：這一步一定不能省略。我就是因為這個問題折騰了一天。囧。。。就怪自己半路出家的吧。
如果省略了會報這樣一個異常
Traceback (most recent call last): File "/usr/local/bin/scrapy", line 9, in <module> load_entry_point('Scrapy==1.0.0rc2', 'console_scripts', 'scrapy')() File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/cmdline.py", line 122, in execute cmds = _get_commands_dict(settings, inproject) File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/cmdline.py", line 50, in _get_commands_dict cmds.update(_get_commands_from_module(cmds_module, inproject)) File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/cmdline.py", line 29, in _get_commands_from_module for cmd in _iter_command_classes(module): File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/cmdline.py", line 20, in _iter_command_classes for module in walk_modules(module_name): File "/usr/local/lib/python2.7/site-packages/Scrapy-1.0.0rc2-py2.7.egg/scrapy/utils/misc.py", line 63, in walk_modules mod = import_module(path) File "/usr/local/lib/python2.7/importlib/__init__.py", line 37, in import_module __import__(name) ImportError: No module named commands
一開始怎么找都找不到原因在哪。耗了我一整天，后來到http://stackoverflow.com/上得到了網友的幫助。再次感謝萬能的互聯網，要是沒有那道牆該是多么的美好呀！扯遠了，繼續回來。
4、settings.py目錄下創建setup.py（這一步去掉也沒影響，不知道官網幫助文檔這么寫有什么具體的意義。）
from setuptools import setup, find_packages setup(name='scrapy-mymodule', entry_points={ 'scrapy.commands': [ 'crawlall=cnblogs.commands:crawlall', ], }, )
這個文件的含義是定義了一個crawlall命令，cnblogs.commands為命令文件目錄，crawlall為命令名。
5. 在settings.py中添加配置：
COMMANDS_MODULE = 'cnblogs.commands'
6. 運行命令scrapy crawlall