Python正则表达式总结

1,正则表达式是用来简洁表述一组字符串的表达式,开头导入re库  import re

2,正则表达式常用操作符

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3,

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4,re的match对象

match对象是一次匹配的结果,包含匹配的很多信息

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5,Re库的贪婪匹配和最小匹配

 Re库默认采用贪婪匹配,即匹配最长字串

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最小匹配 后面加?

 实例1,淘宝商品比价定向爬虫

import re
import requests


def gethtmltext(url):
    try:
        r = requests.get(url, timeout=30)
        r.raise_for_status()
        r.encoding = r.apparent_encoding
        return r.text
    except:
        return ''


def parsepage(ilt, html):
    try:
        plt = re.findall(r'\"view_price\"\:\"[\d\.]*\"', html)
        tlt = re.findall(r'\"raw_title\"\:\".?\"', html)
        for i in range(len(plt)):
            price = eval(plt[i].split(':')[1])
            # eval()除去单双引号
            title = eval(tlt[i].split(':')[1])
            ilt.append([price, title])
    except:
        print("")


def printgoodlist(ilt):
    tplt = "{:4}\t{:8}\t{:16}"
    # 限制长度
    print(tplt.format("序号", "价格", "商品名称"))
    count = 0
    for g in ilt:
        count = count+1
        print(tplt.format(count, g[0], g[1]))


def main():
    depth = 2
    goods = '书包'
    start_url = 'https://s.taobao.com/search?q='+goods
    infolist = []
    for i in range(depth):
        try:
            url = start_url+'$s='+str(44*i)
            html = gethtmltext(url)
            parsepage(infolist, html)
        except:
            continue
    printgoodlist(infolist)


main()

匹配Email地址:\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*

匹配腾讯QQ号:[1-9][0-9]{4,}

匹配日期,只能是 2004-10-22 格式:^\d{4}\-\d{1,2}-\d{1,2}$

匹配国内电话号码:^\d{3}-\d{8}|\d{4}-\d{7,8}$
评注:匹配形式如 010-12345678 或 0571-12345678 或 0831-1234567

匹配中国邮政编码:^[1-9]\d{5}(?!\d)$

匹配身份证:\d{14}(\d{4}|(\d{3}[xX])|\d{1})

匹配中文字符:[\x80-\xff]+ 或者 [\xa1-\xff]+

只能输入汉字:^[\x80-\xff],{0,}$

匹配网址 URL :[a-zA-z]+://[^\s]*

匹配 IP 地址:
((25[0-5]|2[0-4]\d|[01]?\d\d?)\.){3}(25[0-5]|2[0-4]\d|[01]?\d\d?)

匹配完整域名:
[a-zA-Z0-9][-a-zA-Z0-9]{0,62}(\.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+\.?

 只能输入至少n位数字:^\d{n,}$

以上内容转载

实例2,股票数据定向爬虫

import re
from bs4 import BeautifulSoup
import requests
import traceback

def gethtmltext(url):
    try:
        r = requests.get(url, timeout=30)
        r.raise_for_status()
        r.encoding = r.apparent_encoding
        return r.text
    except:
        return ''

def getstocklist(lst,stockurl):
    html=gethtmltext(stockurl)
    # 解析a标签
    soup=BeautifulSoup(html,'html.parser')# html.parser是html解析器,使代码能看懂
    a=soup.find_all('a')
    for i in a:
        try:
            href=i.attrs['href']
            lst.append(re.findall(r"[s][hz]\d{6}",href[0])) 
        except:
            continue

def getstockinfo(lst,stockurl,fpath):
    for stock in lst:
        url=stockurl+stock+".html"
        html=gethtmltext(url)
        try:
            if html=="":
                 continue
            infodict={}
            soup=BeautifulSoup(html,'html.parser')
            stockinfo=soup.find('div',attrs={'class':'stock-bets'})
            name=stockinfo.find_all(attrs={'class':'bets-name'})[0]
            infodict.update({'股票名称':name.text.split()[0]})
            keylist=stockinfo.find_all('dt')
            valuelist=stockinfo.find_all('dd')
            for i in range(len(keylist)):
                key=keylist[i].text
                val=valuelist[i].text
                infodict[key]=val

            with open(fpath,'a',encoding='utf-8') as f:
                f.write(str(infodict)+'\n')
        except:
            traceback.print_exc()
            continue
            

def main():
    # 获取股票链接的主体部分
    stock_list_url='http://quote.eastmoney.com/stocklist.html'
    stock_info_url="https://gupiao.baidu.com/stock/"
    output_file='D://BaiduStockInfo.txt'
    # 股票信息
    slist=[]
    getstocklist(slist,stock_list_url)
    getstockinfo(slist,stock_info_url,output_file)

main()

 

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