输入数组的副本实际上存储在其他某个位置, 并且返回存储在该特定位置的内容, 这是输入数组的副本, 而在视图的情况下, 返回同一内存位置的不同视图。
在本教程的这一部分中, 我们将考虑从某个内存位置生成不同副本和视图的方式。
数组分配
将numpy数组分配给另一个数组不会直接复制原始数组, 而是使另一个数组具有相同的内容和相同的id。它表示对原始数组的引用。在此引用上所做的更改也会反映在原始数组中。
id()函数返回数组的通用标识符, 类似于C中的指针。
考虑以下示例。
例子
import numpy as np
a = np.array([[1, 2, 3, 4], [9, 0, 2, 3], [1, 2, 3, 19]])
print("Original Array:\n", a)
print("\nID of array a:", id(a))
b = a
print("\nmaking copy of the array a")
print("\nID of b:", id(b))
b.shape = 4, 3;
print("\nChanges on b also reflect to a:")
print(a)输出
Original Array:
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
ID of array a: 139663602288640
making copy of the array a
ID of b: 139663602288640
Changes on b also reflect to a:
[[ 1 2 3]
[ 4 9 0]
[ 2 3 1]
[ 2 3 19]]ndarray.view()方法
ndarray.view()方法返回新数组对象, 该对象包含与原始数组相同的内容。由于它是一个新的数组对象, 因此对该对象所做的更改不会反映原始数组。
考虑以下示例。
例子
import numpy as np
a = np.array([[1, 2, 3, 4], [9, 0, 2, 3], [1, 2, 3, 19]])
print("Original Array:\n", a)
print("\nID of array a:", id(a))
b = a.view()
print("\nID of b:", id(b))
print("\nprinting the view b")
print(b)
b.shape = 4, 3;
print("\nChanges made to the view b do not reflect a")
print("\nOriginal array \n", a)
print("\nview\n", b)输出
Original Array:
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
ID of array a: 140280414447456
ID of b: 140280287000656
printing the view b
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
Changes made to the view b do not reflect a
Original array
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
view
[[ 1 2 3]
[ 4 9 0]
[ 2 3 1]
[ 2 3 19]]ndarray.copy()方法
它返回原始数组的深层副本, 该副本不与原始数组共享任何内存。对原始数组的深层副本所做的修改不会反映原始数组。
考虑以下示例。
例子
import numpy as np
a = np.array([[1, 2, 3, 4], [9, 0, 2, 3], [1, 2, 3, 19]])
print("Original Array:\n", a)
print("\nID of array a:", id(a))
b = a.copy()
print("\nID of b:", id(b))
print("\nprinting the deep copy b")
print(b)
b.shape = 4, 3;
print("\nChanges made to the copy b do not reflect a")
print("\nOriginal array \n", a)
print("\nCopy\n", b)输出
Original Array:
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
ID of array a: 139895697586176
ID of b: 139895570139296
printing the deep copy b
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
Changes made to the copy b do not reflect a
Original array
[[ 1 2 3 4]
[ 9 0 2 3]
[ 1 2 3 19]]
Copy
[[ 1 2 3]
[ 4 9 0]
[ 2 3 1]
[ 2 3 19]]来源：
https://www.srcmini02.com/30800.html
