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python爬虫入门（2）re模块-正则表达式

2017-05-21 22:17 896 查看

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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