python 地址引用的陷阱

source = ["one","two"]
li = []

msg = {}

for index in range(len(source)):
    msg[index] = source[index]
    li.append(msg) #字典是可变类型，每次都是修改原有的字典

print li


source2 = ["one","two"]
li2 = []


for index in range(len(source2)):
    li2.append(
        {index:source2[index]}   #每次都是一个新的字典
    )

print li2