BeautifulSoup

import urllib2, re
from  BeautifulSoup import BeautifulSoup

class FlickrPickr(object):
    def __init__(self, url):
        self.url = url
        sq = '%ssizes/sq/' % (url, )
        page = urllib2.urlopen(sq)
        soup = BeautifulSoup(page)
        p = soup.findAll(src=re.compile('jpg$'))
        if p:
            img = p[0]['src']
            bits = img.split('/')
            pic = bits[-1]
            self.baseurl = '/'.join(bits[:-1])
            bits  = pic.split('.')[0].split('_')
            self.id = bits[0]
            self.extra = bits[1]

def get_any(self, endbit):
        return '/'.join([self.baseurl, '_'.join([self.id, self.extra, endbit+'.jpg'])])

def get_square(self):
        return self.get_any('s')

def get_thumb(self):
        return self.get_any('t')

def get_small(self):
        return self.get_any('m')

# doesnt work :(    
    #def get_original(self):
    #    return self.get_any('o')

def get_medium(self):
        return '/'.join([self.baseurl, '_'.join([self.id, self.extra+'.jpg'])])

def main():
    fp = FlickrPickr('http://flickr.com/photos/btbytes/2818112372/')

print fp.get_square()
    print fp.get_thumb()
    print fp.get_small()
    print fp.get_medium()
    print fp.get_original()

if __name__ == '__main__':
    main()