Databases
StackOverflow2013
Postsdbo
POPython Regular Expression: BackReference
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POPython Regular Expression: BackReference
    primarykey
    data
    text
    <p>Here is the Python 2.5 code (which replace the word <code>fox</code> with a link<code>&lt;a href="/fox"&gt;fox&lt;/a&gt;</code>, and it avoided the replacement inside a link):</p> <pre><code>import re content=""" &lt;div&gt; &lt;p&gt;The quick brown &lt;a href='http://en.wikipedia.org/wiki/Fox'&gt;fox&lt;/a&gt; jumped over the lazy Dog&lt;/p&gt; &lt;p&gt;The &lt;a href='http://en.wikipedia.org/wiki/Dog'&gt;dog&lt;/a&gt;, who was, in reality, not so lazy, gave chase to the fox.&lt;/p&gt; &lt;p&gt;See &amp;quot;Dog chase Fox&amp;quot; image for reference:&lt;/p&gt; &lt;img src='dog_chasing_fox.jpg' title='Dog chasing fox'/&gt; &lt;/div&gt; """ p=re.compile(r'(?!((&lt;.*?)|(&lt;a.*?)))(fox)(?!(([^&lt;&gt;]*?)&gt;)|([^&gt;]*?&lt;/a&gt;))',re.IGNORECASE|re.MULTILINE) print p.findall(content) for match in p.finditer(content): print match.groups() output=p.sub(r'&lt;a href="/fox"&gt;\3&lt;/a&gt;',content) print output </code></pre> <p>The output is:</p> <pre><code>[('', '', '', 'fox', '', '.', ''), ('', '', '', 'Fox', '', '', '')] ('', '', None, 'fox', '', '.', '') ('', '', None, 'Fox', None, None, None) Traceback (most recent call last): File "C:/example.py", line 18, in &lt;module&gt; output=p.sub(r'&lt;a href="fox"&gt;\3&lt;/a&gt;',content) File "C:\Python25\lib\re.py", line 274, in filter return sre_parse.expand_template(template, match) File "C:\Python25\lib\sre_parse.py", line 793, in expand_template raise error, "unmatched group" error: unmatched group </code></pre> <ol> <li><p>I am not sure why the backreference <code>\3</code> wont work.</p></li> <li><p><code>(?!((&lt;.*?)|(&lt;a.*?)))(fox)(?!(([^&lt;&gt;]*?)&gt;)|([^&gt;]*?&lt;/a&gt;))</code> works see <a href="http://regexr.com?317bn" rel="nofollow">http://regexr.com?317bn</a> , which is surprising. The first negative lookahead <code>(?!((&lt;.*?)|(&lt;a.*?)))</code> puzzles me. In my opinion, it is not supposed to work. Take the first match it finds, <code>fox</code> in <code>gave chase to the fox.&lt;/p&gt;</code>, there is a <code>&lt;a href='http://en.wikipedia.org/wiki/Dog'&gt;dog&lt;/a&gt;</code> where matches <code>((&lt;.*?)|(&lt;a.*?))</code>, and as a negative lookahead, it should return a FALSE. I am not sure I express myself clearly or not.</p></li> </ol> <p>Thanks a lot!</p> <p>(Note: I hate using BeautifulSoup. I enjoy writing my own regular expression. I know many people here will say Regular expression is not for HTML processing blah blah. But this is a small program, so I prefer Regular expression over BeautifulSoup)</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USSusan Mayer
    1. USSusan Mayer
    plurals
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POPython Regular Expression: BackReference
      1. USMike Pennington
      1. VTFavorite
    1. CO*Why* are you doing this with regex? [Python has such a nice HTML parser.](http://www.crummy.com/software/BeautifulSoup/) Hint: HTML cannot be parsed with regular expressions. You waste your time trying.
      singulars
      1. POPython Regular Expression: BackReference
      1. USTomalak
    2. CO@Tomalak I add a note to the question. this is a tiny program so it wont worth the effort of importing and learning Beautifulsoup. I enjoy regular expression.
      singulars
      1. POPython Regular Expression: BackReference
      1. USSusan Mayer
    3. COSusan, it does not matter in the least if you enjoy regular expressions. This is like playing Golf with a hammer and saying *"I don't have the time to learn what's a 9-iron. I enjoy wielding a hammer."* It is completely the wrong tool for the job. The time it took you to a) try and fail to figure out a regex that works and b) write a question here would have been better invested learning BeautifulSoup. It's not that it would be *hard* or anything. You'd very probably be done already.
      singulars
      1. POPython Regular Expression: BackReference
      1. USTomalak
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload