HTTP Link header parsing routines originally adapted from [Mark Nottingham's gist](https://gist.github.com/mnot/210535) This version adds a `parse_link_value_by_rel` convenience function to address a common use case.

link_header.py

#!/usr/bin/env python

# source: https://gist.github.com/mnot/210535

"""
HTTP Link Header Parsing

Simple routines to parse and manipulate Link headers.
"""

__license__ = """
Copyright (c) 2009 Mark Nottingham
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
"""

import re

TOKEN = r'(?:[^\(\)<>@,;:\\"/\[\]\?={} \t]+?)'
QUOTED_STRING = r'(?:"(?:\\"|[^"])*")'
PARAMETER = r'(?:%(TOKEN)s(?:=(?:%(TOKEN)s|%(QUOTED_STRING)s))?)' % locals()
LINK = r'<[^>]*>\s*(?:;\s*%(PARAMETER)s?\s*)*' % locals()
COMMA = r'(?:\s*(?:,\s*)+)'
LINK_SPLIT = r'%s(?=%s|\s*$)' % (LINK, COMMA)

def _unquotestring(instr):
    if instr[0] == instr[-1] == '"':
        instr = instr[1:-1]
        instr = re.sub(r'\\(.)', r'\1', instr)
    return instr
def _splitstring(instr, item, split):
    if not instr: 
        return []
    return [ h.strip() for h in re.findall(r'%s(?=%s|\s*$)' % (item, split), instr)]

link_splitter = re.compile(LINK_SPLIT)

def parse_link_value(instr):
    """
    Given a link-value (i.e., after separating the header-value on commas), 
    return a dictionary whose keys are link URLs and values are dictionaries
    of the parameters for their associated links.
    
    Note that internationalised parameters (e.g., title*) are 
    NOT percent-decoded.
    
    Also, only the last instance of a given parameter will be included.
    
    For example, 
    
    >>> parse_link_value('</foo>; rel="self"; title*=utf-8\\'de\\'letztes%20Kapitel')
    {'/foo': {'title*': "utf-8'de'letztes%20Kapitel", 'rel': 'self'}}
    
    """
    out = {}
    if not instr: 
        return out
    for link in [h.strip() for h in link_splitter.findall(instr)]:
        url, params = link.split(">", 1)
        url = url[1:]
        param_dict = {}
        for param in _splitstring(params, PARAMETER, "\s*;\s*"):
            try:
                a, v = param.split("=", 1)
                param_dict[a.lower()] = _unquotestring(v)
            except ValueError:
                param_dict[param.lower()] = None
        out[url] = param_dict
    return out
    
def parse_link_value_by_rel(instr):
    """
    This is a must simplified version of the above for the common use-case
    of looking for a particular `rel` value in the list of Link values.

    Given a link-value (i.e., after separating the header-value on commas), 
    return a dictionary whose keys are link `rel` parameter,
    and values are the corresponding URLs.
    
    Notes:
    - Only the last instance of a rel parameter value is included.
    - links with no `rel` parameter (or with an empty value) are ignored.
    - `rel` parameter values are converted to lowercase

    
    For example, 
    
    >>> parse_link_value_by_rel('</foo>; rel="next"; title*=utf-8\\'de\\'letztes%20Kapitel, </bar>')
    {'next': '/foo'}
    
    """
    out = {}
    if not instr: 
        return out
    for link in [h.strip() for h in link_splitter.findall(instr)]:
        url, params = link.split(">", 1)
        url = url[1:]
        param_dict = {}
        for param in _splitstring(params, PARAMETER, "\s*;\s*"):
            try:
                a, v = param.split("=", 1)
                param_dict[a.lower()] = _unquotestring(v)
            except ValueError:
                param_dict[param.lower()] = None
        rel = param_dict.get('rel')
        if not rel:
            continue
        out[rel] = url
    return out
    
    
if __name__ == '__main__':
    import sys
    if len(sys.argv) > 1:
        print parse_link_value(sys.argv[1])