Python 中的语法(. T)

在 SciPy 的多元正态抽样函数的帮助资源中,他们举了以下例子:

x,y = np.random.multivariate_normal(mean,cov,5000).T

我的问题相当基本: 期末考试 T 到底是做什么的?

非常感谢,我知道这很简单,但是在谷歌上很难找到“ . T”。

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The .T accesses the attribute T of the object, which happens to be a NumPy array. The T attribute is the transpose of the array, see the documentation.

Apparently you are creating random coordinates in the plane. The output of multivariate_normal() might look like this:

>>> np.random.multivariate_normal([0, 0], [[1, 0], [0, 1]], 5)
array([[ 0.59589335,  0.97741328],
[-0.58597307,  0.56733234],
[-0.69164572,  0.17840394],
[-0.24992978, -2.57494471],
[ 0.38896689,  0.82221377]])

The transpose of this matrix is:

array([[ 0.59589335, -0.58597307, -0.69164572, -0.24992978,  0.38896689],
[ 0.97741328,  0.56733234,  0.17840394, -2.57494471,  0.82221377]])

which can be conveniently separated in x and y parts by sequence unpacking.

.T is just np.transpose(). Best of luck

Example

import numpy as np
a = [[1, 2, 3]]
b = np.array(a).T  # ndarray.T The transposed array. [[1,2,3]] -> [[1][2][3]]
print("a=", a, "\nb=", b)
for i in range(3):
print(" a=", a[0][i])  # prints  1 2 3
for i in range(3):
print(" b=", b[i][0])  # prints  1 2 3