list 的拷贝问题：

1,

a
[1, 2]
b=a[:]
b
[1, 2]
b[0]=20
b
[20, 2]
a
[1, 2]

2,

import copy

c=copy.copy(a)
c
[1, 2]
c[1]=30
c
[1, 30]
a
[1, 2]
b
[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}