文章来源:如何整合Flask&Scrapy? - 代码领悟code05.com
提问:如何整合Flask&Scrapy?
我正在使用scrapy来获取数据,我想使用flask web框架在网页中显示结果。 但不知道如何调用flask应用程序中的蜘蛛。 我已经尝试使用CrawlerProcess
来调用我的蜘蛛,但我得到了这样的错误:
ValueError
ValueError: signal only works in main thread
Traceback (most recent call last)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1836, in __call__
return self.wsgi_app(environ, start_response)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1820, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Library/Python/2.7/site-packages/flask/app.py", line 1403, in handle_exception
reraise(exc_type, exc_value, tb)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
response = self.full_dispatch_request()
File "/Library/Python/2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/Library/Python/2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
rv = self.dispatch_request()
File "/Library/Python/2.7/site-packages/flask/app.py", line 1461, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/Users/Rabbit/PycharmProjects/Flask_template/FlaskTemplate.py", line 102, in index
process = CrawlerProcess()
File "/Library/Python/2.7/site-packages/scrapy/crawler.py", line 210, in __init__
install_shutdown_handlers(self._signal_shutdown)
File "/Library/Python/2.7/site-packages/scrapy/utils/ossignal.py", line 21, in install_shutdown_handlers
reactor._handleSignals()
File "/Library/Python/2.7/site-packages/twisted/internet/posixbase.py", line 295, in _handleSignals
_SignalReactorMixin._handleSignals(self)
File "/Library/Python/2.7/site-packages/twisted/internet/base.py", line 1154, in _handleSignals
signal.signal(signal.SIGINT, self.sigInt)
ValueError: signal only works in main thread
我的scrapy代码是这样的:
class EPGD(Item):
genID = Field()
genID_url = Field()
taxID = Field()
taxID_url = Field()
familyID = Field()
familyID_url = Field()
chromosome = Field()
symbol = Field()
description = Field()
class EPGD_spider(Spider):
name = "EPGD"
allowed_domains = ["epgd.biosino.org"]
term = "man"
start_urls = ["http://epgd.biosino.org/EPGD/search/textsearch.jsp?textquery="+term+"&submit=Feeling+Lucky"]
db = DB_Con()
collection = db.getcollection(name, term)
def parse(self, response):
sel = Selector(response)
sites = sel.xpath('//tr[@class="odd"]|//tr[@class="even"]')
url_list = []
base_url = "http://epgd.biosino.org/EPGD"
for site in sites:
item = EPGD()
item['genID'] = map(unicode.strip, site.xpath('td[1]/a/text()').extract())
item['genID_url'] = base_url+map(unicode.strip, site.xpath('td[1]/a/@href').extract())[0][2:]
item['taxID'] = map(unicode.strip, site.xpath('td[2]/a/text()').extract())
item['taxID_url'] = map(unicode.strip, site.xpath('td[2]/a/@href').extract())
item['familyID'] = map(unicode.strip, site.xpath('td[3]/a/text()').extract())
item['familyID_url'] = base_url+map(unicode.strip, site.xpath('td[3]/a/@href').extract())[0][2:]
item['chromosome'] = map(unicode.strip, site.xpath('td[4]/text()').extract())
item['symbol'] = map(unicode.strip, site.xpath('td[5]/text()').extract())
item['description'] = map(unicode.strip, site.xpath('td[6]/text()').extract())
self.collection.update({"genID":item['genID']}, dict(item), upsert=True)
yield item
sel_tmp = Selector(response)
link = sel_tmp.xpath('//span[@id="quickPage"]')
for site in link:
url_list.append(site.xpath('a/@href').extract())
for i in range(len(url_list[0])):
if cmp(url_list[0][i], "#") == 0:
if i+1 < len(url_list[0]):
print url_list[0][i+1]
actual_url = "http://epgd.biosino.org/EPGD/search/" + url_list[0][i+1]
yield Request(actual_url, callback=self.parse)
break
else:
print "The index is out of range!"
我的flask代码是这样的:
@app.route('/', methods=['GET', 'POST'])
def index():
process = CrawlerProcess()
process.crawl(EPGD_spider)
return redirect(url_for('details'))
@app.route('/details', methods = ['GET'])
def epgd():
if request.method == 'GET':
results = db['EPGD_test'].find()
json_results= []
for result in results:
json_results.append(result)
return toJson(json_results)
在使用flask web框架时,如何调用我的scrapy spiders?
回答:
在你的蜘蛛前面添加HTTP服务器并不那么容易。 有几个选择。
1. Python子进程
如果你真的局限于Flask,如果你不能使用其他任何东西,那么将Scrapy与Flask集成的唯一方法是为每个蜘蛛抓取启动外部进程,正如其他答案所建议的那样(请注意,你的子进程需要在适当的Scrapy项目目录中产生)。
所有示例的目录结构应该是这样的,我正在使用dirbot测试项目
> tree -L 1
├── dirbot
├── README.rst
├── scrapy.cfg
├── server.py
└── setup.py
下面是在新进程中启动Scrapy的代码示例:
# server.py
import subprocess
from flask import Flask
app = Flask(__name__)
@app.route('/')
def hello_world():
"""
Run spider in another process and store items in file. Simply issue command:
> scrapy crawl dmoz -o "output.json"
wait for this command to finish, and read output.json to client.
"""
spider_name = "dmoz"
subprocess.check_output(['scrapy', 'crawl', spider_name, "-o", "output.json"])
with open("output.json") as items_file:
return items_file.read()
if __name__ == '__main__':
app.run(debug=True)
以上保存为server.py 并访问localhost:5000,您应该能够看到刮掉的项目。
2. 扭曲-克莱因+Scrapy
其他更好的方法是使用一些现有的项目,该项目将Twisted与Werkzeug集成,并显示类似于Flask的API,例如Twisted-Klein。 Twisted-Klein将允许您在与web服务器相同的进程中异步运行蜘蛛。 更好的是它不会阻止每个请求,它允许您简单地从HTTP路由请求处理程序返回Scrapy/Twisted deferreds。
以下snippet将Twisted-Klein与Scrapy集成在一起,请注意,您需要创建自己的CrawlerRunner基类,以便crawler将收集项目并将其返回给caller。 这个选项更高级一点,你正在运行Scrapy蜘蛛与Python服务器相同的进程,项目不存储在文件中,而是存储在内存中(所以没有磁盘写入/读取,如前面的例子)。 最重要的是它是异步的,它都在一个扭曲的反应器中运行。
# server.py
import json
from klein import route, run
from scrapy import signals
from scrapy.crawler import CrawlerRunner
from dirbot.spiders.dmoz import DmozSpider
class MyCrawlerRunner(CrawlerRunner):
"""
Crawler object that collects items and returns output after finishing crawl.
"""
def crawl(self, crawler_or_spidercls, *args, **kwargs):
# keep all items scraped
self.items = []
# create crawler (Same as in base CrawlerProcess)
crawler = self.create_crawler(crawler_or_spidercls)
# handle each item scraped
crawler.signals.connect(self.item_scraped, signals.item_scraped)
# create Twisted.Deferred launching crawl
dfd = self._crawl(crawler, *args, **kwargs)
# add callback - when crawl is done cal return_items
dfd.addCallback(self.return_items)
return dfd
def item_scraped(self, item, response, spider):
self.items.append(item)
def return_items(self, result):
return self.items
def return_spider_output(output):
"""
:param output: items scraped by CrawlerRunner
:return: json with list of items
"""
# this just turns items into dictionaries
# you may want to use Scrapy JSON serializer here
return json.dumps([dict(item) for item in output])
@route("/")
def schedule(request):
runner = MyCrawlerRunner()
spider = DmozSpider()
deferred = runner.crawl(spider)
deferred.addCallback(return_spider_output)
return deferred
run("localhost", 8080)
以上保存在文件中server.py 并在您的Scrapy项目目录中找到它, 现在打开localhost:8080,它将启动dmoz spider并将抓取的项目作为json返回到浏览器。
3. [医]刮锥器
当您尝试在蜘蛛面前添加HTTP应用程序时,会出现一些问题。 例如,您有时需要处理蜘蛛日志(在某些情况下可能需要它们),您需要以某种方式处理蜘蛛异常等。 有些项目允许您以更简单的方式向蜘蛛添加HTTP API,例如ScrapyRT。 这是一个应用程序,它将HTTP服务器添加到您的Scrapy蜘蛛中,并为您处理所有问题(例如处理日志记录,处理蜘蛛错误等)。
所以安装ScrapyRT后你只需要做:
> scrapyrt
在您的Scrapy项目目录中,它将为您启动http服务器侦听请求。 然后你访问http://localhost:9080/crawl.json?spider_name=dmoz&url=http://alfa.com它应该启动你的蜘蛛为你爬行的url给出。
免责声明:我是ScrapyRt的作者之一。
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