Stage6--Python简单爬虫

正则表达式简单介绍

正则表达式(regular expression)描述了一种字符串匹配的模式，可以用来检查一个串是否含有某种子串、将匹配的子串做替换或者从某个串中取出符合某个条件的子串等。

字符 [a-z]

数字 [0-9] 或 \b

* 匹配前面的子表达式零次或多次

+ 匹配前面的子表达式一次或多次

? 匹配前面的子表达式零次或一次

一个简单爬虫例子

import re
import urllib.request

url = "http://mall.csdn.net/coin"

savePath = "G:/QQData/"

def getHtml(url):
    page = urllib.request.urlopen(url)
    html = page.read().decode('utf-8')
    return html

def getImg(html):
    reg = r'http:\/\/img.bss.csdn.net\/[0-9]+\.jpg'
    imgre = re.compile(reg)
    imglist = re.findall(imgre, html)
    return imglist;

def saveImg(url):
    conn = urllib.request.urlopen(url)
    file = open(savePath + getFileName(url), 'wb')
    file.write(conn.read())
    file.close()
    return

def getFileName(url):
    reg = r'[a-z0-9]+\.jpg'
    matchObj = re.search(reg, url)
    if matchObj:
        return matchObj.group()
    return

html = str(getHtml(url));
imgurls = getImg(html);

for imgurl in imgurls:
    print(imgurl)
    saveImg(imgurl)

这个例子很简单，里面的正则简单的到没有，是爬取CSDN U币商城的图片，很容易看懂。

可以自定义正则和Url的爬虫

from tkinter import *
import re
import urllib.request

savePath = "G:/QQData/"

class ControllPanel(Frame):

    default_url = "http://www.xingyongshe.com/man/ddfeijibei"
    default_regix = r'<img src="(.+)&amp;w=228&amp;q=90&amp;type=jpg'
    __status_label = None  #私有属性
    url_input = None
    regix_input = None

    def __init__(self, master):
        Frame.__init__(self, master, width=360, height=260)
        self.master = master
        self.pack()
        self.add_urlarea()
        self.add_regixarea()
        self.add_buttonarea()
        self.add_statusbar()

    def add_urlarea(self):
        urlAreaFrame = Frame(self)
        urlAreaFrame.pack(pady=20)
        label = Label(urlAreaFrame, text="网址:")
        label.pack(side=LEFT)
        self.url_input = Entry(urlAreaFrame, width=40)
        self.url_input.insert(0, ControllPanel.default_url)
        self.url_input.pack(side=RIGHT)

    def add_regixarea(self):
        regixAreaFrame = Frame(self)
        regixAreaFrame.pack()
        label = Label(regixAreaFrame, text="正则:")
        label.pack(side=LEFT)
        self.regix_input = Entry(regixAreaFrame, width=40)
        self.regix_input.insert(0, self.default_regix)     #注意这里的访问方式和上面方式不同
        self.regix_input.pack(side=RIGHT)

    def add_buttonarea(self):
        buttonAreaFrame = Frame(self)
        buttonAreaFrame.pack(pady=40)
        verify_button = Button(buttonAreaFrame, text="验证正则", command=self.verifyRegix)
        verify_button.pack(padx=50, side=LEFT)
        start_button = Button(buttonAreaFrame, text="开始爬取", command=self.startRun)
        start_button.pack(padx=50, side=RIGHT)

    def verifyRegix(self):
        if self.url_input == None or self.regix_input == None:
            return
        url = self.url_input.get()
        regix = self.regix_input.get()
        runfunction = RunFunction(url, regix)
        imgurls = runfunction.verifyRegix()
        if len(imgurls) > 0:
            self.setStatus("有%d张图片可以爬取", len(imgurls))
        for imgurl in imgurls:
            print(imgurl)
        return imgurls

    def startRun(self):
        imgurls = self.verifyRegix()
        runfunction = RunFunction(None, None)
        size = runfunction.runTask(imgurls)
        self.setStatus("爬取了%d张图片放在了" + savePath, size)

    def add_statusbar(self):
        statusBarFrame = Frame(self.master)
        statusBarFrame.pack(side=BOTTOM, fill=X)
        self.status_label = Label(statusBarFrame, bd=1, relief=SUNKEN, anchor=W)
        self.status_label.pack(fill=X)

    def setStatus(self, format, *args):
        if self.status_label == None:
            return
        self.status_label.config(text=format % args)
        self.status_label.update_idletasks()
        return

    def clearStatus(self):
        self.status_label.config(text="")
        self.status_label.update_idletasks()

class RunFunction:

    def __init__(self, url, regix):
        self.url = url
        self.regix = regix

    def getHtml(self, url):
        page = urllib.request.urlopen(url)
        html = page.read().decode('utf-8')
        return html

    def getImg(self, html, reg):
        imgre = re.compile(reg)
        imglist = re.findall(imgre, html)
        return imglist;

    def saveImg(self, url):
        conn = urllib.request.urlopen(url)
        file = open(savePath + self.getFileName(url), 'wb')
        file.write(conn.read())
        file.close()
        return

    def getFileName(self, url):
        reg = r'[a-z0-9]+\.jpg'
        matchObj = re.search(reg, url)
        if matchObj:
            return matchObj.group()
        return

    def verifyRegix(self):
        html = str(self.getHtml(self.url))
        imgurls = self.getImg(html, self.regix)
        return imgurls

    def runTask(self):
        imgurls = self.verifyRegix(self.url, self.regix)
        for imgurl in imgurls:
            self.saveImg(imgurl)
        return len(imgurls)

    def runTask(self, imgurls):
        for imgurl in imgurls:
            self.saveImg(imgurl)
        return len(imgurls)

root = Tk()
root.title("爬虫管理窗口")

#让窗口居中显示
scnWidth, scnHeight = root.maxsize()
tmpcnf = '%dx%d+%d+%d'%(308, 101, (scnWidth-308)/2, (scnHeight-101)/2)
root.geometry(tmpcnf)

root.maxsize(600, 300)
root.minsize(360, 220)
#root.resizable(False, False) #让窗口尺寸不变

controllPanel = ControllPanel(root)
controllPanel.setStatus("等待爬取……")

root.mainloop()
root.destroy()