python 深拷贝与浅拷贝

python 中变量赋值有三种方式

1. 直接赋值，如

   a = 1
   b = a
   c = [1,3,4,6]
   d = c

2. 浅拷贝

   import copy
   c = [1,3,4,6]
   d = c.copy()

3. 深拷贝

   import copy
   c = [1,3,4,6]
   d = copy.deepcopy(c)