I saw a function numpy.fill_diagonal which assigns same value for diagonal elements. But I want to assign different random values for each diagonal elements. How can I do it in python ? May be using scipy or other libraries ?

解决方案

You can use np.diag_indices to get those indices and then simply index into the array with those and assign values.

Here's a sample run to illustrate it -

In [86]: arr # Input array

Out[86]:

array([[13, 69, 35, 98, 16],

[93, 42, 72, 51, 65],

[51, 33, 96, 43, 53],

[15, 26, 16, 17, 52],

[31, 54, 29, 95, 80]])

# Get row, col indices

In [87]: row,col = np.diag_indices(arr.shape[0])

# Assign values, let's say from an array to illustrate

In [88]: arr[row,col] = np.array([100,200,300,400,500])

In [89]: arr

Out[89]:

array([[100, 69, 35, 98, 16],

[ 93, 200, 72, 51, 65],

[ 51, 33, 300, 43, 53],

[ 15, 26, 16, 400, 52],

[ 31, 54, 29, 95, 500]])

You can also use np.diag_indices_from and probably would be more idomatic, like so -

row, col = np.diag_indices_from(arr)

Note : The tried function would work just fine. This is discussed in a previous Q&A - Numpy modify ndarray diagonal too.