Cannot find data from string using regex while string.find() works just fine

Question

import re
import urllib
p = urllib.urlopen("http://sprunge.us/QZhU")
page = p.read()
pos = page.find("<h2><span>")
print page[pos:pos+48]
c = re.compile(r'<h2><span>(.*)</span>')
print c.match(page).group(1)

When I run it:

shadyabhi@archlinux $ python2 temp.py 
<h2><span>House.S08E02.HDTV.XviD-LOL.avi</span> 
Traceback (most recent call last):
  File "temp.py", line 8, in <module>
    print c.match(page).group(1)
AttributeError: 'NoneType' object has no attribute 'group'
shadyabhi@archlinux $

If I can find a string using string.find then what is the problem when I use regex. I have tried looking http://docs.python.org/howto/regex.html#regex-howto but no help.

NPE · Accepted Answer · 2011-10-14 13:18:28Z

6

match only matches at the beginning of the string. Use search, finditer or findall.

Also note that * is greedy. You might want to change your regex to r'<h2><span>(.*?)</span>'.

In summary, the following works for me:

import re
import urllib
p = urllib.urlopen("http://sprunge.us/QZhU")
page = p.read()
pos = page.find("<h2><span>")
print page[pos:pos+48]
c = re.compile(r'<h2><span>(.*?)</span>')
print c.search(page).group(1)

answered Oct 14, 2011 at 13:18

NPE

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4 Comments

shadyabhi Over a year ago

Does by beginning mean "till the first newline comes"? Also, please tell what happened when I add "?"? It matches zero or 1 repetition of previous RE. Whats previoud RE? Isn't the while string a RE?

NPE Over a year ago

@shadyabhi: No, it means that the first character of the string must be the first character of the match. Matches beginning at the second character and thereafter are not considered. On the words, for match to work, the HTML document must begin with <h2><span>..., not contain it somewhere in the middle.

shadyabhi Over a year ago

Also, please tell what happened when I add "?"? It matches zero or 1 repetition of previous RE. Whats previous RE? Isn't the whole string a RE?

NPE Over a year ago

@shadyabhi: *? is a single operator. It matches as few characters as possible, whereas * matches as many as possible. See docs.python.org/library/re.html#regular-expression-syntax

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