我的结果

爬取“深圳赶集二手——二手商品——个人——真实个人”，链接28195条，详情28159条

结果.png

我的代码

模块.png
说明：
all_category：从首页获取所有子项链接
deal_each_cate：包含两个重要函数：①提取商品链接；②提取商品详情
counts：计数器

main.py

from multiprocessing import Pool
from deal_each_cate import get_all_urls, get_goods_info
from all_category import ganji_channel
from deal_each_cate import ganji_cate_url
from deal_each_cate import ganji_second_hand

# step1
if __name__ == '__main__':
    # 断点程序
    # ganji_channel这个collection里面包含所有频道1至80页的链接
    all_channel = [page['channel'] for page in ganji_channel.find()]
    # ganji_cate_url里除了包含商品的链接，也包含了这个链接出现页面的链接
    channel_done = [page['channel'] for page in ganji_cate_url.find()]
    # 挑出还没有爬的频道页面
    rest_of_channel = set(all_channel) - set(channel_done)
    print(len(rest_of_channel))
    pool = Pool(processes=4)
    pool.map(get_all_urls, rest_of_channel)

# step2
if __name__ == '__main__':
    # 断点程序
    db_urls = [item['url'] for item in ganji_cate_url.find()]
    info_urls = [item['url'] for item in ganji_second_hand.find()]
    x = set(db_urls)
    y = set(info_urls)
    rest_of_urls = x - y
    print(len(rest_of_urls))
    # print(len(rest_of_urls)) 29693
    # 4个进程
    if rest_of_urls:
        pool = Pool(processes=4)
        pool.map(get_goods_info, rest_of_urls)
    else:
        print('It\'s done')

all_category.py

from bs4 import BeautifulSoup
import requests, time, pymongo

client = pymongo.MongoClient('localhost', 27017)
walden = client['walden']
ganji_channel = walden['ganji_channel']

# cate_list = []
# def get_all_cates():
#     wu_page = 'http://sz.ganji.com/wu/'
#     time.sleep(1)
#     web_data = requests.get(wu_page)
#     soup = BeautifulSoup(web_data.text, 'lxml')
#     for category in soup.select('.fenlei dt a'):
#         category = category.get('href')
#         cate_list.append(category)
#     # print(len(cate_list))
#     # print(cate_list)

cate_list = ['/jiaju/', '/rirongbaihuo/', '/shouji/', '/bangong/', '/nongyongpin/', '/jiadian/',
             '/ershoubijibendiannao/', '/ruanjiantushu/', '/yingyouyunfu/', '/diannao/', '/xianzhilipin/',
             '/fushixiaobaxuemao/',
             '/meironghuazhuang/', '/shuma/', '/laonianyongpin/', '/xuniwupin/', '/qitawupin/', '/ershoufree/',
             '/wupinjiaohuan/']

# for item in cate_list:
#     for i in range(1, 81):
#         channel_page = 'http://sz.ganji.com{}o{}/'.format(item, i)
#         ganji_channel.insert_one({'channel':channel_page})

# print(ganji_channel.find().count())

deal_each_cate.py

# -*- coding:'utf-8' -*-
from bs4 import BeautifulSoup
import requests, time, pymongo, random

client = pymongo.MongoClient('localhost', 27017)
walden = client['walden']
ganji_cate_url = walden['ganji_cate_url']
ganji_second_hand = walden['ganji_second_hand']

headers = {'User-Agent': 'Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.116 Safari/537.36'}

# spider1
def get_all_urls(url):
    try:
        web_data = requests.get(url, headers=headers, timeout=7)
        soup = BeautifulSoup(web_data.text, 'lxml')
        # 直到某一页开始没有个人信息就停止
        if soup.find(text='真实个人'):
            # 获取链接
            for info_url in soup.select('.zz-til a'):
                info_url = info_url.get('href').split('&')[0]
                # 处理链接，否则不能顺利爬取商品详情
                useful_url = 'http://zhuanzhuan.58.com/detail/' + info_url.split('=')[-1] + 'z.shtml'
                # 查重, 把ganji_cate_url打开，取出每一条记录的url组成set
                if useful_url not in set(map(lambda x: x['url'], ganji_cate_url.find())):
                    ganji_cate_url.insert_one({'url': useful_url, 'channel': url})
                    print(useful_url)
                else:
                    pass
        else:
            print('nothing')
            # 没有个人信息了
            pass
    except Exception as e:
        print(e)


# spider2
def get_goods_info(url):
    try:
        web_data = requests.get(url, headers=headers, timeout=6)
        soup = BeautifulSoup(web_data.text, 'lxml')
        print(url)
        if soup.find(id='fail'):
            print('fail')
        elif soup.find(text='商品已下架'):
            print('商品已下架')
        else:
            # 提取信息
            title = soup.select('.info_titile')[0].get_text()
            price = soup.select('.price_now i')[0].get_text()
            region = soup.select('.palce_li i')[0].get_text() if soup.find(class_='palce_li') else None
            desc = soup.select('.baby_kuang p')[0].get_text()
            # 写入数据库
            ganji_second_hand.insert_one(
                {'title': title, 'price': price, 'region': region, 'describe': desc, 'url': url})
            print({'title': title, 'price': price, 'region': region, 'describe': desc, 'url': url})
    except Exception as e:
            print(e)

counts.py

# -*- coding:'utf-8' -*-
import time
from deal_each_cate import ganji_cate_url
from deal_each_cate import ganji_second_hand

# step1
while True:
   print(ganji_cate_url.find().count())
   time.sleep(5)

# step2
while True:
    print(ganji_second_hand.find().count())
    time.sleep(5)

我的感想：

• 完成时间：从昨天到今天早上（实际上我真的不想回忆昨天，好深的坑啊）
• 昨天应该是网络有问题，老是报错，今早上一次性完成（详情页面大约每秒15个）
• 断点程度，实际上就是用减法排除那些不再需要爬取的部分，重点在于构建减数和被减数（在不同的数据库中保留相同格式的部分，比如 url，作为类似标记）
• 计数器挺有意思的，写一个小模块单独运行（开两个cmd）
• “真实个人”的商品链接点进去其实是“转转”，链接格式如：
  url = 'http://m.zhuanzhuan.58.com/Mzhuanzhuan/zzWebInfo/zzganji/zzpc/detailPc.html?infoId=762113121520779268'
  必须要转成为另外的格式，才能爬到商品详情（关键在 id）：
  url = 'http://zhuanzhuan.58.com/detail/762113121520779268z.shtml'