mongoDB 3.2之后默认是使用wireTiger引擎

在启动时更改存储引擎： 

　　mongod --storageEngine mmapv1 --dbpath d:\data\db

这样就可以解决mongvue不能查看文档的问题啦！

项目流程（步骤）：

前去准备（安装scrapy pymongo mongodb ）

　1. 生成项目目录： scrapy startproject  stack

　2.itmes　　　

from scrapy import Item,Field


class StackItem(Item):
    title = Field()
    url = Field()

　3. 创建爬虫

from scrapy import Spider
from scrapy.selector import Selector
from stack.items import StackItem

class StackSpider(Spider):
    name = "stack"
    allowed_domains = ["stackoverflow.com"]
    start_urls = [
        "http://stackoverflow.com/questions?pagesize=50&sort=newest",
    ]

    def parse(self, response):
        questions = response.xpath(‘//div[@class="summary"]/h3‘)

        for question in questions:
            item = StackItem()
            item[‘title‘] = question.xpath(
                ‘a[@class="question-hyperlink"]/text()‘).extract()[0]
            item[‘url‘] = question.xpath(
                ‘a[@class="question-hyperlink"]/@href‘).extract()[0]
            yield item

　4.学会使用xpath selectors 进行数据的提取

　5.存储数据到mongo中

　　5.1 setting.py

ITEM_PIPELINES = {
   ‘stack.pipelines.MongoDBPipeline‘: 300,
}

MONGODB_SERVER = "localhost"
MONGODB_PORT = 27017
MONGODB_DB = "stackoverflow"
MONGODB_COLLECTION = "questions"

　　5.2 pipelines.py

import pymongo

from scrapy.conf import settings
from scrapy.exceptions import  DropItem
from scrapy import log

class MongoDBPipeline(object):
    def __init__(self):
        connection = pymongo.MongoClient(
            settings[‘MONGODB_SERVER‘],
            settings[‘MONGODB_PORT‘]
        )
        db = connection[settings[‘MONGODB_DB‘]]
        self.collection = db[settings[‘MONGODB_COLLECTION‘]]

    def process_item(self, item, spider):
        valid = True
        for data in item:
            if not data:
                valid = False
                raise DropItem("Missing {0}!".format(data))
        if valid:
            self.collection.insert(dict(item))
            log.msg("Question added to MongoDB database!",
                    level=log.DEBUG, spider=spider)

        return item

　6. 启动爬虫 main.py

from scrapy import cmdline

cmdline.execute(‘scrapy crawl stack‘.split())

效果图

python 第二周（第十一天） 我的python成长记 一个月搞定python数据挖掘！(19) -scrapy + mongo