无法为矩阵中的条目分配值

Question

I'm trying to create a complex matrix and assign the 0,0 entry to the value of 1+0j. Here's the code I wrote:

import numpy as n
import cmath

M=n.zeros((5,5),dtype=complex)
M[0:0]=1+0j
print M

However, after executing, the 0,0 entry is still zero:

[[ 0.+0.j  0.+0.j  0.+0.j  0.+0.j  0.+0.j]
 [ 0.+0.j  0.+0.j  0.+0.j  0.+0.j  0.+0.j]
 [ 0.+0.j  0.+0.j  0.+0.j  0.+0.j  0.+0.j]
 [ 0.+0.j  0.+0.j  0.+0.j  0.+0.j  0.+0.j]
 [ 0.+0.j  0.+0.j  0.+0.j  0.+0.j  0.+0.j]]

What's wrong with my code? What's the proper way to do it?

Answer 1

You just need to code your matrix element reference like this:

    M[0,0]=1+0j

The syntax M[0:0] would mean the first sublist to just before the first sublist, ie an empty element. Try evaluating M[0:1]

    >>>> M[0:1]
    array([[ 1.+0.j,  0.+0.j,  0.+0.j,  0.+0.j,  0.+0.j]])