python爬虫入门（2）re模块-正则表达式

正则表达式

---

search //匹配第一次遇到符合规则的

匹配IP地址

1. import re
2. re.search(r'(([01]{0,1}\d{0,1}\d|2[0-4]\d|25[0-5])\.){3}([01]{0,1}\d{0,1}\d|2[0-4]\d|25[0-5])','192.168.1.1')

 

findall:匹配所有，把所有匹配到的字符放到一个列表中并返回

1. >>> p = re.compile('\d+')
2. >>> p.findall('3只小甲鱼，15条腿，多出的3条在哪里？')
3. ['3','15','3']

 

 

编译正则表达式   re.compile()

1. >>>import re
2. >>> p = re.compile('[a-z]+')
3. >>> p
4. re.compile('[a-z]+')
6. >>> p.match("")
7. >>>print(p.match(""))
8. None
10. >>> m = p.match('fishc')
11. >>> m
12. <_sre.SRE_Match object; span=(0,5), match='fishc'>

方法：

group()   返回匹配的字符串

start()    返回匹配的开始位置

end()      返回匹配的结束位置

span()    返回一个元组表示匹配位置（开始，结束）

1. >>> m.group()
2. 'fishc'
3. >>> m.start()
4. 0
5. >>> m.end()
6. 5
7. >>> m.span()
8. (0,5)

 

编译标志，详情请查看http://bbs.fishc.com/thread-57207-1-1.html

1. 设置了编译标志符
2. charref = re.compile(r"""
3. &[#] # 开始数字引用
4. (
5. 0[0-7]+ # 八进制格式
6. | [0-9]+ # 十进制格式
7. | x[0-9a-fA-F]+ # 十六进制格式
8. )
9. ; # 结尾分号
10. """, re.VERBOSE)

1. 未设置编译标志符
2. charref = re.compile("&#(0[0-7]+|[0-9]+|x[0-9a-fA-F]+);")

 

---

示例1：从代理网站上爬IP地址

    import urllib.request
    import re
    def open_url(url):
        req = urllib.request.Request(url)
        req.add_header('User-Agent','Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.97 Safari/537.36')
        page = urllib.request.urlopen(req)#获取页面内容
        html = page.read().decode('utf-8')#解码页面内容
        return html

    def get_img(html):
        p = r'(?:(?:[0,1]?\d?\d|2[0-4]\d|25[0-5])\.){3}(?:[0,1]?\d?\d|2[0-4]\d|25[0-5])' #匹配IP地址
        iplist = re.findall(p,html)
        for each in iplist:
            print(each)

    if __name__ =='__main__':
        url ="http://www.xicidaili.com/"
        get_img(open_url(url))

 

示例2：爬取妹纸图

import urllib.request
import os
import re

def save_imgs(folder, img_addrs):
    for each in img_addrs:
        filename = each.split('/')[-1]
        with open(filename, 'wb') as f:
            img = url_open(each)
            f.write(img)
        print(1)
    print(2)

def url_open(url):
    reg = urllib.request.Request(url)
    reg.add_header('User-Agent',
                   'Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36')
    response = urllib.request.urlopen(url)
    html = response.read()

    return html

def get_page(url):
    html = url_open(url).decode('utf-8')

    # a = html.find('current-comment-page')+23
    a = re.search(r'\[\d{1,4}\]', html)
    a = a.group()
    b = len(a)
    a = a[1:b - 1]
    return a

def find_imgs(url):
    html = url_open(url).decode('utf-8')
    img_addrs = []
    a = html.find('img src=')
    while a != -1:
        b = html.find('.jpg', a, a + 255)
        if b != -1:
            if 'lanya' in html[a + 9:b + 4]:
                pass
            else:
                img_addrs.append('http:' + html[a + 9:b + 4])
        else:
            b = a + 9
        a = html.find('img src=', b)
    print(img_addrs)
    return img_addrs

def download_mm(folder='ooxx', pages=4, star=0):
    os.mkdir(folder)
    os.chdir(folder)

    url = 'http://jandan.net/ooxx/'  # 妹子图地址
    # url = 'http://jandan.net/pic/' #无聊图地址
    if star != 0:
        page_num = star
    else:
        page_num = int(get_page(url))
    for i in range(pages):
        page_num -= 1
        page_url = url + 'page-' + str(page_num) + '#comments'

        img_addrs = find_imgs(page_url)

        save_imgs(folder, img_addrs)

        print(page_url)

if __name__ == '__main__':
    download_mm()

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