python对象的复制问题

list 的拷贝问题：

 1 >>> a
 2 [1, 2]
 3 >>> b=a[:]
 4 >>> b
 5 [1, 2]
 6 >>> b[0]=20
 7 >>> b
 8 [20, 2]
 9 >>> a
10 [1, 2]

 1 import copy
 2 >>> c=copy.copy(a)
 3 >>> c
 4 [1, 2]
 5 >>> c[1]=30
 6 >>> c
 7 [1, 30]
 8 >>> a
 9 [1, 2]
10 >>> b
11 [20, 2]

dictionary:

 1 >>> a=[('he',1),('wo','jia')]
 2 >>> p=dict(a)
 3 >>> p
 4 {'wo': 'jia', 'he': 1}
 5 >>> b=p.copy()
 6 >>> b
 7 {'wo': 'jia', 'he': 1}
 8 >>> b['wo']='ja'
 9 >>> b
10 {'wo': 'ja', 'he': 1}
11 >>> p
12 {'wo': 'jia', 'he': 1}