Python 爬蟲知識點

1、基礎知識

一、HTML分析

二、urllib爬取

導入urilib包（Python3.5.2）

三、urllib保存網頁

import urllib.request
url = "http://www.cnblogs.com/wj204/p/6151070.html"
html = urllib.request.urlopen(url).read()
fh=open("F:/20_Python/3000_Data/2.html","wb")
fh.write(html)
fh.close()

四、模擬瀏覽器

import urllib.request
url="http://www.cnblogs.com/"
headers=("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.22 Safari/537.36 SE 2.X MetaSr 1.0")
opener=urllib.request.build_opener()
opener.addheaders=[headers]
data=opener.open(url).read()
fh=open("F:/20_Python/3000_Data/1.html","wb")
fh.write(data)
fh.close()

 

五、urllib保存圖片

 使用  http://www.bejson.com/  查看存儲在JS中的Json數據g_page_config

import re
import urllib.request
keyWord = "Python機器學習"
keyWord2 = urllib.request.quote(keyWord)
headers = ("User-Agent","MMozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.104 Safari/537.36 Core/1.53.1708.400 QQBrowser/9.5.9635.400")
opener = urllib.request.build_opener()
opener.addheaders = [headers]
urllib.request.install_opener(opener)
url = "https://s.taobao.com/search?q=" + keyWord2 + "&imgfile=&commend=all&ssid=s5-e&search_type=item&sourceId=tb.index&spm=a21bo.50862.201856-taobao-item.1&ie=utf8&initiative_id=tbindexz_20161214"
data = urllib.request.urlopen(url).read().decode("utf-8","ignore")
pat = 'pic_url":"//(.*?)"'#注意，該數據不在Html代碼之中，在全局腳本g_page_config
imageList = re.compile(pat).findall(data)
for j in range(0,len(imageList)):
    try:
        curImage = imageList[j]
        curImageUrl = "http://" + curImage
        file="F:/20_Python/3000_Data/" +  str(j) + ".jpg"
        print(file)
        urllib.request.urlretrieve(curImageUrl,filename=file)
    except urllib.error.URLError as e:
        if hasattr(e,"code"):
            print(e.code)
        if hasattr(e,"reason"):
            print(e.reason)
    except Exception as e:
        print(e)

 

六、正則表達式

 經常使用正則表達式爬取網頁信息及分析HTML標籤總結 http://blog.csdn.net/eastmount/article/details/51082253

 如對Python機器學習的正則分析：

pat = 'pic_url":"//(.*?)"'

re.compile(pat).findall(data)

提取（.*?）,位於pic_url":"//和"之中

 

如對糗事百科的正則分析：

pat='<div class="content">.*?<span>(.*?)</span>.*?</div>'
datalist=re.compile(pat,re.S).findall(pagedata)

 

七、IP代理

 須要靠譜穩定的IP地址，找到合適的代理替換 proxy_addr

import urllib.request
import random
def use_proxy(url,proxy_addr):
    proxy=urllib.request.ProxyHandler({"http":random.choice(proxy_addr)})
    headers = ("User-Agent","Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/49.0.2623.22 Safari/537.36 SE 2.X MetaSr 1.0")
    opener=urllib.request.build_opener(proxy,urllib.request.HTTPHandler)
    opener.addheaders = [headers]
    urllib.request.install_opener(opener)
    data=urllib.request.urlopen(url).read().decode("utf-8","ignore")
    return data
proxy_addr=["45.64.166.142:8080","80.1.116.80:80","196.15.141.27:8080","47.88.6.158:8118","125.209.97.190  :8080"]
url="http://cuiqingcai.com/1319.html" #http://proxy.com.ru
data=use_proxy(url,proxy_addr)
print(len(data))

八、抓包分析

 

九、多線程爬取

 

import threading

class DownPage(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)
    def run(self):
        print("處理下載業務業務")

downTask = DownPage()
downTask.start()

十、異常處理

 見：urllib保存圖片，使用try：except：捕獲異常

 

十一、XPath

 http://www.cnblogs.com/defineconst/p/6181333.html

2、Scrapy安裝關聯包

 PyCharm---》File---》Settings---》Project..........