[Python 3.8 ~] Rewrite arrays etc. at the same time as definition [tips]

Introduction

-I want to make array initialization compact-

That wish can be realized. Yes, it's 3.8 ~.

How to do

(Variable name:=Definition)[slice] =Change

Note) Even if you do not slice, an error will be thrown if you do not add [:] etc.

For example

** ~ I want to define a matrix in which 1 to 9 are lined up diagonally plus 1 every 3 rows ~ **

Such a mysterious situation is also this street

import numpy as np
(x:=np.diag(range(10)))[::3] += 1
x

out

array([[ 1,  1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 0,  1,  0,  0,  0,  0,  0,  0,  0,  0],
       [ 0,  0,  2,  0,  0,  0,  0,  0,  0,  0],
       [ 1,  1,  1,  4,  1,  1,  1,  1,  1,  1],
       [ 0,  0,  0,  0,  4,  0,  0,  0,  0,  0],
       [ 0,  0,  0,  0,  0,  5,  0,  0,  0,  0],
       [ 1,  1,  1,  1,  1,  1,  7,  1,  1,  1],
       [ 0,  0,  0,  0,  0,  0,  0,  7,  0,  0],
       [ 0,  0,  0,  0,  0,  0,  0,  0,  8,  0],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1, 10]])

For example

** ~ I want to draw a matrix with my left and right inverted on a square matrix with 1 to 9 lined up diagonally ~ **

Even in such a case, this street

import numpy as np
(x:=np.diag(range(10)))[:] -= x[:, ::-1]
x

out

array([[ 0,  0,  0,  0,  0,  0,  0,  0,  0,  0],
       [ 0,  1,  0,  0,  0,  0,  0,  0, -1,  0],
       [ 0,  0,  2,  0,  0,  0,  0, -2,  0,  0],
       [ 0,  0,  0,  3,  0,  0, -3,  0,  0,  0],
       [ 0,  0,  0,  0,  4, -4,  0,  0,  0,  0],
       [ 0,  0,  0,  0, -5,  5,  0,  0,  0,  0],
       [ 0,  0,  0, -6,  0,  0,  6,  0,  0,  0],
       [ 0,  0, -7,  0,  0,  0,  0,  7,  0,  0],
       [ 0, -8,  0,  0,  0,  0,  0,  0,  8,  0],
       [-9,  0,  0,  0,  0,  0,  0,  0,  0,  9]])

finally

The number of convenient walrus operator utilization series is increasing ...