np.array()賦值

當一個array的維度很大時，進行賦值會比較費時間

比如下面的簡單賦值會花費約184s.

import numpy as np
import time

beginn = time.time()
a = np.zeros((10, 10, 10))
b = [1, 1, 2, 3]
for i in range(100):
    for j in range(4):
        if i > 50:
            a = 1*3
        a = np.ones((46, 2000, 2000))
        a[j] += np.ones((2000, 2000))
print(time.time()-beginn)
print("a")