从html字符串中删除python regex中不需要的模式

Question

I have to parse the custom vin number from html

I get few wrong matched number also.

 .....
 <meta name="google-site-verification" content="l4du7Ao9MH6TM2nJ5L54qqWoXWcuOkdeqhXCADgKErc" />
 <meta name="msvalidate.01" content="FAD32C2469C51767894EB50068D37244" />
     .....
  <div class="hproduct auto chevrolet" data-classification="primary" data- vin="3GNDA23D18S647673" data-make="Chevrolet" >

 .....
 </dd></dl><dl class='vin'><dt>VIN:</dt><dd>3GNDA23D18S647673</dd></dl> <span 
 ....... etc....

This is the piece of html which contains required portion

When I apply my regex in python

import re
re.findall("([0-9A-Z]{8}[0-9xX]{1}[1-9A-Y^U]{1}[0-9A-Z]{2}[0-9]{5})",html)

I get the required results along with the unwanted data like

['FAD32C2469C517678',
 '3GNDA23D18S647673',
 '3GNDA23D18S647673']

FAD32C2469C517678 is unwanted one.

How can I get rid of this unwanted patteren in regex in python?

Answer 1

Please, use a parser:

import lxml.html as lh
doc=lh.fromstring(html)
doc.xpath('.//@vin')

out

["3GNDA23D18S647673"]

EDIT: if vin is always an attribute, but you don't know the name, you can try:

doc.xpath('.//@*[string-length() = "17"]') # get's attrs with lenght 17

or with regex, if you really,really have to:

import re
re.findall('"([A-Z0-9]{17})"',html)

Answer 2

You should really use an HTML parser but for a quick fix use the regexp (?<=vin=")[^"]+ :

>>> import re
>>> html = """.....
...  <meta name="google-site-verification" content="l4du7Ao9MH6TM2nJ5L54qqWoXWcuOkdeqhXCADgKErc" />
...  <meta name="msvalidate.01" content="FAD32C2469C51767894EB50068D37244" />
...      .....
...   <div class="hproduct auto chevrolet" data-classification="primary" data- vin="3GNDA23D18S647673" data-make="Chevrolet" >
... 
...  .....
...  </dd></dl><dl class='vin'><dt>VIN:</dt><dd>3GNDA23D18S647673</dd></dl> <span 
...  ....... etc...."""

>>> re.findall('(?<=vin=")[^"]+',html)
['3GNDA23D18S647673']

This uses positive lookbehind to match [^"]+ (one or more characters not a double quote) after the string after vin=" .

If you want to more strict in your match you could use your regexp in combination with the positive lookbehind:

re.findall('(?<=vin=")[0-9A-Z]{8}[0-9xX]{1}[1-9A-Y^U]{1}[0-9A-Z]{2}[0-9]{5}',html)
['3GNDA23D18S647673']