Concatenate multi value into one record.

Question

I joined two tables together and what I like to do is concatenate multi vaule in one records without duplicated value.

1. Input Table
   
   Table name: TAXLOT_ZONE
   TID ZONE
   1 A
   1 A
   1 B
   1 C
   2 D
   2 D
   2 E
   3 A
   3 B
   4 C
   5 D
   

2. Desirable output table looks like;
   
   table name: Taxlot_zone_out
   TID ZONE
   1 A, B, C
   2 D, E
   3 A, B
   4 C
   5 D
   

Answer 1

Assuming your table is in sorted order and is iterable, you can use itertools.groupby to group rows with the same first element.

l = [(1, 'A'), (1, 'A'), (1, 'B'), (1, 'C'),
     (2, 'D'), (2, 'D'), (2, 'E'),
     (3, 'A'), (3, 'B'),
     (4, 'C'),
     (5, 'D')]

from itertools import groupby
from operator import itemgetter
result = [(taxlot, list(set(v for k,v in g)))
          for taxlot, g in groupby(l, itemgetter(0))]

Result:

[(1, ['A', 'C', 'B']),
 (2, ['E', 'D']),
 (3, ['A', 'B']),
 (4, ['C']),
 (5, ['D'])]