如何在python中简化for循环

Question

I have this piece of Python code that fills up a 2d matrix in a for loop

img=zeros((len(bins_x),len(bins_y)))

for i in arange(0,len(ix)):
   img[ix[i]][iy[i]]=dummy[i]

Is it possible to use a vectorial operation for the last two lines of code? Is there also something that might speed up the calculation?

Answer 1

如果是ix，我是索引序列：

img[ix, iy] = dummy

Answer 2

It might be useful to use numpy . In particular, the reshape method might be useful. Here is an example (adapted from the second link):

>>> import numpy as np
>>> a = np.array([1,2,3,4,5,6])
>>> np.reshape(a, (3,2))
array([[1, 2],
       [3, 4],
       [5, 6]])