python 中如何格式化数据

(
    (1, '10.121.1.1:4730'), 
    (2, '127.0.0.1:4730'),
    (3, '127.0.0.1:4730')
)

如何格式化为以下格式 用python

{
    '10.121.1.1:4730':
        [(1, '10.121.1.1:4730')], 
    '127.0.0.1:4730':
        [(2, '127.0.0.1:4730'), (3, '127.0.0.1:4730')]
}

---

虽然已经有采纳了，但还是可以提下：
看到这个setdefault，就想起collections.defaultdict，功能比setdefault更强大，接受的参数可以使默认初始化类型，也可以是函数。其实也可以更简洁

from collections import defaultdict 
ips = (
    (1, '10.121.1.1:4730'),
    (2, '127.0.0.1:4730'),
    (3, '127.0.0.1:4730')
   )
 result = defaultdict(list)
 for v, k in ips:
     result[k].append((v, k))

---

上面的是数组，下面的是dict()序列号后的JSON。把数组遍历然后拼接成字典，输出JSON即可。

import json

a = (
    (1, '10.121.1.1:4730'), 
    (2, '127.0.0.1:4730'),
    (3, '127.0.0.1:4730')
)

b = dict()
for value in a :
    number = value[0]
    address = value[1]
    if address not in b :
        b[address] = []
    b[address].append([number, address])

print json.dumps(b)

---

根据@dokelung，@松林两位老兄提供的建议改进

ips = (
    (1, '10.121.1.1:4730'),
    (2, '127.0.0.1:4730'),
    (3, '127.0.0.1:4730')
)

dic = {}
for v, k in ips:
    dic.setdefault(k, []).append((v, k))

print dic