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Jan 4th, 2009

find() and rfind() questions

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First post so thanks in advance for any help. I am looking to pull the anchor text from a series of links in some html. I am doing this with find() and rfind():

[code]linkend=users.find("</a>:")
linkstart=users.rfind(">",0,linkend)[code]

My question is that once I have found the first link, how do I then continue to move on from that point? If I were to run this in a for loop 50 times it would just give me the first link 50 times, rather than finding all 50 links on the page, which is what I'm after. Thanks for your help everybody.

betatype

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Jan 4th, 2009

Re: find() and rfind() questions

Supply a starting index for str.find() and update it each iteration. Example:

Python Syntax (Toggle Plain Text)
users = '''Users
<a>User 1</a>
<a>User 2</a>
<a>User 3</a>
<a>User 4</a>
<a>User 5</a>
'''
 
userList = []
idx = 0
while True:
    linkstart=users.find("<a>",idx)
    linkend=users.find("</a>", idx)
    if -1 in [linkstart,linkend]:
        break
    else:
        userList.append(users[linkstart+3:linkend])
        idx = linkend+4
 
print userList
users = '''Users
<a>User 1</a>
<a>User 2</a>
<a>User 3</a>
<a>User 4</a>
<a>User 5</a>
'''

userList = []
idx = 0
while True:
    linkstart=users.find("<a>",idx)
    linkend=users.find("</a>", idx)
    if -1 in [linkstart,linkend]:
        break
    else:
        userList.append(users[linkstart+3:linkend])
        idx = linkend+4

print userList

Output:

Python Syntax (Toggle Plain Text)
>>> ['User 1', 'User 2', 'User 3', 'User 4', 'User 5']
>>> ['User 1', 'User 2', 'User 3', 'User 4', 'User 5']

solsteel

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Jan 4th, 2009

Re: find() and rfind() questions

Genius! Thanks so much.

betatype

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Jan 4th, 2009

Re: find() and rfind() questions

Is this for a homework assignment? I just want to know if you're allowed to use any Python tool you want, or if you're limited to what you've covered in class.

I'm sure there is a way to do it with find, but why don't you check out this tutorial on HTMLParser. It includes an example of how to do what you're trying to do.
http://cis.poly.edu/cs912/parsing.txt

mn_kthompson

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No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

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