l=[['id0', 'pyt'], ['id0', 'hon'], ['id1', 'aiu'], ['id1', 'eo']]
from itertools import groupby
for r in [(k, ''.join([item[1] for item in i])) for k,i in groupby(l, key=lambda x:x[0])]: print(*r)

はい、オレが優勝