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

import re
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

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

编译正则表达式 re.compile()

>>>import re
>>> p = re.compile('[a-z]+')
>>> p
re.compile('[a-z]+')
>>> p.match("")
>>>print(p.match(""))
None
>>> m = p.match('fishc')
>>> m
<_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）

>>> m.group()
'fishc'
>>> m.start()
0
>>> m.end()
5
>>> m.span()
(0,5)

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

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

未设置编译标志符
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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python爬虫入门（2）re模块-正则表达式

正则表达式

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