import numpy as np

# define arrays in numpy:

testarray1D = np.array([1, 5, 41.3, 2.0])

print(f'type(testarray1D): {type(testarray1D)}\n')

testarray2D = np.array([[4, 9, 8, 3],

[2, 6, 3, 2],

[1, 1, 7, 4]])

# get dimensions of testarray2D:

dim = testarray2D.shape

print(f'dim: {dim}\n')

# access elements by indices:

third_elem = testarray1D[2]

print(f'third_elem: {third_elem}\n')

second_third_elem = testarray2D[1, 2] # element in 2nd row and 3rd column

print(f'second_third_elem: {second_third_elem}\n')

second_to_third_col = testarray2D[:, 1:3] # each row in the 2nd and 3rd column

print(f'second_to_third_col: \n{second_to_third_col}\n')

# access elements by lists:

first_third_elem = testarray1D[[0, 2]]

print(f'first_third_elem: {first_third_elem}\n')

# same with Boolean lists:

first_third_elem2 = testarray1D[[True, False, True, False]]

print(f'first_third_elem2: {first_third_elem2}\n')

k = np.array([[True, False, False, False],

[False, False, True, False],

[True, False, True, False]])

elem_by_index = testarray2D[k] # 1st elem in 1st row, 3rd elem in 2nd row...

print(f'elem_by_index: {elem_by_index}\n')