A Python method to map protein IDs via the UniProt mapping service

uniprot_mapping.py

import urllib
import urllib2

def uniprot_mapping(fromtype, totype, identifier):
    """Takes an identifier, and types of identifier 
    (to and from), and calls the UniProt mapping service"""
    base = 'http://www.uniprot.org'
    tool = 'mapping'
    params = {'from':fromtype,
                'to':totype,
                'format':'tab',
                'query':identifier,
    }
    #urllib turns the dictionary params into an encoded url suffix
    data = urllib.urlencode(params)
    #construct the UniProt URL
    url = base+'/'+tool+'?'+data
    #and grab the mapping
    response = urllib2.urlopen(url)
    #response.read() provides tab-delimited output of the mapping
    return response.read()

if __name__ == '__main__':
    print uniprot_mapping('EMBL_ID', 'ID', 'X02469')
    #see http://www.uniprot.org/faq/28#id_mapping_examples for from&to codes