python 全局變量錯誤

python_global_variable.py

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#
#   Author  :   Rhapsodyzs
#   E-mail  :   zs1213yh@gmail.com
#   Date    :   14/01/20 00:42:52
#   Desc    :    全局變量錯誤
#



c = [(1,2), (2, 3), (3, 4)]
a = []
b = {} # 將此放在循環外
for i in c:
    b = {} #將此語句放入循環內部
    b['user'] = i[0]
    b['dd'] = i[1]
    a.append(b)

print a