Python String Replace: Keywords into URLs

Question

I am going to replace some keywords with urls in a string, for example,

content.replace("Google","<a href="http://www.google.com">Google</a>")

However, I only want to replace keywords with urls ONLY if not already wrapped in a url.

The content is simple HTML:

<p><b>This is an example!</b></p><p>I love <a href="http://www.google.com">Google</a></p><p><a href="http://www.google.com"><img src="/google.jpg" /></a></p>

Mainly <a> and <img> tags.

The main question: How to determine if a keyword is already wrapped in a <a> or <img> tag?

Here is a similar question in PHP find and replace keywords with urls ONLY if not already wrapped in a url, but the answer is not an efficient one.

Is there some better solutions in Python? Better with code examples. Thanks!

Answer 1

I am using Beatiful Soup for parsing my HTML, since parsing HTML with regex can..be proven tricky. If you use beautiful soup you can toy with previous_sibling and previous_element figure out what you need.

You interact in this fashion:

soup.find_all('img')

Answer 2

As Chris-Top said, BeautifulSoup is the way to go:

from BeautifulSoup import BeautifulSoup, Tag, NavigableString
import re    

html = """
<div>
    <p>The quick brown <a href='http://en.wikipedia.org/wiki/Dog'>fox</a> jumped over the lazy Dog</p>
    <p>The <a href='http://en.wikipedia.org/wiki/Dog'>dog</a>, who was, in reality, not so lazy, gave chase to the fox.</p>
    <p>See image for reference:</p>
    <img src='dog_chasing_fox.jpg' title='Dog chasing fox'/>
</div>
"""
soup = BeautifulSoup(html)

#search term, url reference
keywords = [("dog","http://en.wikipedia.org/wiki/Dog"),
            ("fox","http://en.wikipedia.org/wiki/Fox")]

def insertLinks(string_value,string_href):
    for t in soup.findAll(text=re.compile(string_value, re.IGNORECASE)):
            if t.parent.name !='a':
                    a = Tag('a', name='a')
                    a['href'] = string_href
                    a.insert(0, NavigableString(string_value))
                    string_list = re.compile(string_value, re.IGNORECASE).split(t)
                    replacement_text = soup.new_string(string_list[0])
                    t.replace_with(replacement_text)
                    replacement_text.insert_after(a)
                    a.insert_after(soup.new_string(string_list[1]))


for word in keywords:
    insertLinks(word[0],word[1])

print soup

Will yield:

<div>
    <p>The quick brown <a href="http://en.wikipedia.org/wiki/Dog">fox</a> jumped over the lazy <a href="http://en.wikipedia.org/wiki/Dog">dog</a></p>
    <p>The <a href="http://en.wikipedia.org/wiki/Dog">dog</a>, who was, in reality, not so lazy, gave chase to the <a href="http://en.wikipedia.org/wiki/Fox">fox</a>.</p>
    <p>See image for reference:</p>
    <img src="dog_chasing_fox.jpg" title="Dog chasing fox"/>
</div>

Answer 3

You can try adding a regular expression as mentioned in the previous post. First check your string against a regular expression to check whether it has already been wrapped in a URL. This should be pretty easy as a simple call to the re library and its search() method should do the trick.

Here is a nice tutorial if you need for regular expressions and the search method specifically: http://www.tutorialspoint.com/python/python_reg_expressions.htm

After you check the string to see whether it is already wrapped in a URL or not, you can call the replace function if it is not already wrapped in a URL.

Here is a quick example that I wrote:

    import re

    x = "<a href=""http://www.google.com"">Google</a>"
    y = 'Google'

    def checkURL(string):
        if re.search(r'<a href.+', string):
            print "URL Wrapped Already"
            print string
        else:
            string = string.replace('Google', "<a href=""http://www.google.com"">Google</a>")
            print "URL Not Wrapped:"
            print string

    checkURL(x)
    checkURL(y)

I hope this answers your question!