一个网络爬虫的分析

#-*- coding: UTF-8 -*- 
import time
import leveldb
from urllib.parse import quote_plus
import re
import json
import itertools
import sys
import requests
from queue import Queue
from threading import Thread
 
URL_BASE = ‘http://s.m.taobao.com/search?q={}&n=200&m=api4h5&style=list&page={}‘
 
def url_get(url):
    # print(‘GET ‘ + url)
    header = dict()
    header[‘Accept‘] = ‘text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8‘
    header[‘Accept-Encoding‘] = ‘gzip,deflate,sdch‘
    header[‘Accept-Language‘] = ‘en-US,en;q=0.8‘
    header[‘Connection‘] = ‘keep-alive‘
    header[‘DNT‘] = ‘1‘
    #header[‘User-Agent‘] = ‘Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.71 Safari/537.36‘
    header[‘User-Agent‘] = ‘Mozilla/12.0 (compatible; MSIE 8.0; Windows NT)‘
    return requests.get(url, timeout = 5, headers = header).text
 
def item_thread(cate_queue, db_cate, db_item):
    while True:
        try:
            cate = cate_queue.get()
            post_exist = True
            try:
                state = db_cate.Get(cate.encode(‘utf-8‘))
                if state != b‘OK‘: post_exist = False
            except:
                post_exist = False
            if post_exist == True:
                print(‘cate-{}: {} already exists ... Ignore‘.format(cate, title))
                continue
            db_cate.Put(cate.encode(‘utf-8‘), b‘crawling‘)
            for item_page in itertools.count(1):
                url = URL_BASE.format(quote_plus(cate), item_page)
                for tr in range(5):
                    try:
                        items_obj = json.loads(url_get(url))
                        break
                    except KeyboardInterrupt:
                        quit()
                    except Exception as e:
                        if tr == 4: raise e
                if len(items_obj[‘listItem‘]) == 0: break                       
                for item in items_obj[‘listItem‘]:
                    item_obj = dict(
                        _id = int(item[‘itemNumId‘]),
                        name = item[‘name‘],
                        price = float(item[‘price‘]),
                        query = cate,
                        category = int(item[‘category‘]) if item[‘category‘] != ‘‘ else 0,
                        nick = item[‘nick‘],
                        area = item[‘area‘])
                    db_item.Put(str(item_obj[‘_id‘]).encode(‘utf-8‘),
                                json.dumps(item_obj, ensure_ascii = False).encode(‘utf-8‘))
 
                print(‘Get {} items from {}: {}‘.format(len(items_obj[‘listItem‘]), cate, item_page))
 
                if ‘nav‘ in items_obj:
                    for na in items_obj[‘nav‘][‘navCatList‘]:
                        try:
                            db_cate.Get(na[‘name‘].encode(‘utf-8‘))
                        except:
                            db_cate.Put(na[‘name‘].encode(‘utf-8‘), b‘waiting‘)
            db_cate.Put(cate.encode(‘utf-8‘), b‘OK‘)
            print(cate, ‘OK‘)
        except KeyboardInterrupt:
            break
        except Exception as e:
            print(‘An {} exception occured‘.format(e))
 
def cate_thread(cate_queue, db_cate):
    while True:
        try:
            for key, value in db_cate.RangeIter():
                if value != b‘OK‘:
                    print(‘CateThread: put {} into queue‘.format(key.decode(‘utf-8‘)))
                    cate_queue.put(key.decode(‘utf-8‘))
            time.sleep(10)
        except KeyboardInterrupt:
            break
        except Exception as e:
            print(‘CateThread: {}‘.format(e))
 
if __name__ == ‘__main__‘:
    db_cate = leveldb.LevelDB(‘./taobao-cate‘)
    db_item = leveldb.LevelDB(‘./taobao-item‘)

    orig_cate = ‘正装‘.encode(‘gb2312‘)
    try:
        db_cate.Get(orig_cate.encode(‘utf-8‘))
    except:
        db_cate.Put(orig_cate.encode(‘utf-8‘), b‘waiting‘)
    cate_queue = Queue(maxsize = 1000)
    cate_th = Thread(target = cate_thread, args = (cate_queue, db_cate))
    cate_th.start()
    item_th = [Thread(target = item_thread, args = (cate_queue, db_cate, db_item)) for _ in range(5)]
    for item_t in item_th:
        item_t.start()
    cate_th.join()