numpy中array和asarray

numpy中array和asarray

1. array和asarray都可以将结构数据转化为ndarray，但是主要区别就是当数据源是ndarray时，array会copy出一个副本，占用新的内存，属于深拷贝。asarray是浅拷贝。

   import numpy as np
   
   a = np.array([1,2,3])
   b = np.array(a)
   c = np.asarray(a)
   print(f'before change,array:{a}\narray: {b}\nasarray: {c}')
   
   a[0] = 4
   print(f'after change,array:{a}\narray: {b}\nasarray: {c}')
   

   >>before change,array:[1 2 3]
   array: [1 2 3]
   asarray: [1 2 3]
   after change,array:[4 2 3]
   array: [1 2 3]
   asarray: [4 2 3]

2. 当数据源是list时,可以看到两者都是对元数据的拷贝，并且改变元数据不会造成两者的变化

   a = [1, 2, 3]
   b = np.array(a)
   c = np.asarray(a)
   print(f'before change,list:{a}\narray: {b}\nasarray: {c}')
   
   a[0] = 4
   print(f'after change,list:{a}\narray: {b}\nasarray: {c}')
   

   >>before change,list:[1, 2, 3]
   array: [1 2 3]
   asarray: [1 2 3]
   after change,list:[4, 2, 3]
   array: [1 2 3]
   asarray: [1 2 3]