Slicing URL with Python

Question

I am working with a huge list of URL's. Just a quick question I have trying to slice a part of the URL out, see below:

http://www.domainname.com/page?CONTENT_ITEM_ID=1234&param2&param3

How could I slice out:

http://www.domainname.com/page?CONTENT_ITEM_ID=1234

Sometimes there is more than two parameters after the CONTENT_ITEM_ID and the ID is different each time, I am thinking it can be done by finding the first & and then slicing off the chars before that &, not quite sure how to do this tho.

Cheers

Answer 1

Use the urlparse module. Check this function:

import urlparse

def process_url(url, keep_params=('CONTENT_ITEM_ID=',)):
    parsed= urlparse.urlsplit(url)
    filtered_query= '&'.join(
        qry_item
        for qry_item in parsed.query.split('&')
        if qry_item.startswith(keep_params))
    return urlparse.urlunsplit(parsed[:3] + (filtered_query,) + parsed[4:])

In your example:

>>> process_url(a)
'http://www.domainname.com/page?CONTENT_ITEM_ID=1234'

This function has the added bonus that it's easier to use if you decide that you also want some more query parameters, or if the order of the parameters is not fixed, as in:

>>> url='http://www.domainname.com/page?other_value=xx&param3&CONTENT_ITEM_ID=1234&param1'
>>> process_url(url, ('CONTENT_ITEM_ID', 'other_value'))
'http://www.domainname.com/page?other_value=xx&CONTENT_ITEM_ID=1234'

Answer 2

Look at the urllib2 file name question for some discussion of this topic.

Also see the "Python Find Question" question.

Answer 3

Parsin URL is never as simple I it seems to be, that's why there are the urlparse and urllib modules.

E.G :

import urllib
url ="http://www.domainname.com/page?CONTENT_ITEM_ID=1234&param2&param3"
query = urllib.splitquery(url)
result = "?".join((query[0], query[1].split("&")[0]))
print result
'http://www.domainname.com/page?CONTENT_ITEM_ID=1234'

This is still not 100 % reliable, but much more than splitting it yourself because there are a lot of valid url format that you and me don't know and discover one day in error logs.

Answer 4

The quick and dirty solution is this:

>>> "http://something.com/page?CONTENT_ITEM_ID=1234&param3".split("&")[0]
'http://something.com/page?CONTENT_ITEM_ID=1234'

Answer 5

import re
url = 'http://www.domainname.com/page?CONTENT_ITEM_ID=1234&param2&param3'
m = re.search('(.*?)&', url)
print m.group(1)

Answer 6

An ancient question, but still, I'd like to remark that query string paramenters can also be separated by ';' not only '&'.