parsing a nested dictionary : I would like to parse the following nested dictionary for all URL entries. They should be written into a list. How can I do this?

    {u'_id': ObjectId('56a22819ffd6f'),
     u'books': [{u'id': {u'id': u'4311'},
       u'link': {u'name': u'Operating Business',
        u'url': u'http://ffff'}},
      {u'id': {u'id': u'4310'},
       u'link': {u'name': u'Operating Business',
        u'url': u'http://zzzzz'}},
      {u'id': {u'id': u'7462'},
       u'link': {u'name': u'European Credit Trading',
        u'url': u'http://xxxx'}},
      {u'id': {u'id': u'3258'},
       u'link': {u'name': u'Operating Business',
        u'url': u'http://dddddd'}},
      {u'id': {u'id': u'7463'},
       u'link': {u'name': u'US Credit Trading',
        u'url': u'http://aaaaa'}}],
     u'created': datetime.datetime(2016, 1, 2, 13, 1, 12, 744000),
     u'id': u'lingering-smoke',
     u'valuationDate': datetime.datetime(170, 1, 1, 0, 0, 16, 821000)}