如何用另一个numpy数组填充numpy数组 [英] How to fill numpy array with another numpy array

问题描述

我有一个空的numpy数组，另一个有值。我想用填充的x填充空的numpy数组。
因此，当x = 3时，（最初为空的数组）看起来像 [[populated_array]，[populated_array]，[populated_array]]

I have an empty numpy array, and another one populated with values. I want to fill the empty numpy array with the populated one, x times. So, when x = 3, the (originally empty array) would look like [[populated_array],[populated_array], [populated_array]]

其中populated_array每次都是相同的值/数组。
我已经尝试过

Where populated_array is the same value/array each time. I have tried this

a = np.empty(3)
a.fill(np.array([4,6,6,1]))

但是得到这个

ValueError: Input object to FillWithScalar is not a scalar

并想要这个

[[4,6,6,1],[4,6,6,1],[4,6,6,1]]

为任何帮助而欢呼。

推荐答案

tile 和重复是方便的函数，可通过各种方式重复数组：

tile and repeat are handy functions when you want to repeat an array in various ways:

In [233]: np.tile(np.array([4,6,6,1]),(3,1))
Out[233]: 
array([[4, 6, 6, 1],
       [4, 6, 6, 1],
       [4, 6, 6, 1]])

在失败时，请注意 fill 的文档：

On the failure, note the docs for fill:

a.fill(value)

Fill the array with a scalar value.

np.array（[4,6,6,1]）不是标量值。 a 初始化为3个元素 float 数组。

np.array([4,6,6,1]) is not a scalar value. a was initialized as a 3 element float array.

只要形状正确，就可以为数组的元素分配值：

It is possible to assign values to elements of an array, provided the shapes are right:

In [241]: a=np.empty(3)
In [242]: a[:]=np.array([1,2,3])    # 3 numbers into 3 slots
In [243]: a
Out[243]: array([ 1.,  2.,  3.])
In [244]: a=np.empty((3,4))
In [245]: a[:]=np.array([1,2,3,4])   # 4 numbers into 4 columns
In [246]: a
Out[246]: 
array([[ 1.,  2.,  3.,  4.],
       [ 1.,  2.,  3.,  4.],
       [ 1.,  2.,  3.,  4.]])

此 fill 与对象类型数组一起使用，但结果却大不相同，应谨慎使用：

This fill works with an object type array, but the result is quite different, and should be used with considerable caution:

In [247]: a=np.empty(3, object)
In [248]: a
Out[248]: array([None, None, None], dtype=object)
In [249]: a.fill(np.array([1,2,3,4]))
In [250]: a
Out[250]: array([array([1, 2, 3, 4]), array([1, 2, 3, 4]), array([1, 2, 3, 4])], dtype=object)

此（3，）数组与其他方法生成的（3,4）数组不同。对象数组的每个元素都是指向同一事物的指针。更改 a 的一个元素中的值会更改所有元素中的值（因为它们是同一对象）。

This (3,) array is not the same as the (3,4) array produced by other methods. Each element of the object array is a pointer to the same thing. Changing a value in one element of a changes that value in all the elements (because they are the same object).

In [251]: a[0][3]=5
In [252]: a
Out[252]: array([array([1, 2, 3, 5]), array([1, 2, 3, 5]), array([1, 2, 3, 5])], dtype=object)

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