>>> import numpy as np

>>> xs = np.arange(1, 5)
>>> xs
array([1, 2, 3, 4])
>>> xs = xs.reshape(2, 2)
>>> xs
array([[1, 2],
       [3, 4]])
>>> xs.dtype
dtype('int32')

>>> xs[0, 0]
1
>>> xs[0, 0] = 1.3
>>> xs[0, 0]
1
>>> xs
array([[1, 2],
       [3, 4]])

>>> xs[0, 0] = 3.3
>>> xs
array([[3, 2],
       [3, 4]])

>>> ys = xs.astype(dtype=float)
>>> ys
array([[3., 2.],
       [3., 4.]])
>>> ys[0, 0]
3.0
>>> ys[0, 0] = 3.3
>>> ys[0, 0]
3.3
>>> ys
array([[3.3, 2. ],
       [3. , 4. ]])
>>> ys.dtype
dtype('float64')