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。