How to convert a column or row matrix to a diagonal matrix in Python?

  For getting your desired output ,you can try python diagonal matrix method like this:

import numpy as np

a = np.array([1,2,3,4])
d = np.diag(a)
# or simpler: d = np.diag([1,2,3,4])
print(d)
Results in:
[[1 0 0 0]
 [0 2 0 0]
 [0 0 3 0]
 [0 0 0 4]]
If you have a row vector, you can do this:
a = np.array([[1, 2, 3, 4]])
d = np.diag(a[0])
Results in:
[[1 0 0 0]
 [0 2 0 0]
 [0 0 3 0]
 [0 0 0 4]]
For the given matrix in the question:
import numpy as np
a = np.matrix([1,2,3,4])
d = np.diag(a.A1)
print (d)
The result is again:
[[1 0 0 0]
 [0 2 0 0]
 [0 0 3 0]
 [0 0 0 4]]