因为不知道你那串是字符串还是什么, 所以我这里先按照字符串的方式去实现

l = '0:13 1:9 2:14 3:19 4:12 3:19'
d = {}
result = []
for _ in l.split():
    key = _.split(':')[0]
    if key not in d:
        d[key] = _
        result.append(d[key])

print(result)
print(result)

# 输出
['0:13', '1:9', '2:14', '3:19', '4:12']

from itertools import groupby

str = '0:13 1:9 2:14 3:19 4:12 3:6'
lst = str.split()
lst.sort()

g_lst = [list(g)[0] for k, g in groupby(lst, key=lambda x: x.split(':')[0])]
print g_lst

#['0:13', '1:9', '2:14', '3:19', '4:12']