Excercise and Answers

1) Create an arbitrary one dimensional array called "v".
Ans:>>>import numpy as np
>>>v=np.arange(5)




2) Create a new array which consists of the odd indices of previously created array "v"?
Ans:
>>>import numpy as np
>>>v=np.arange(5)
>>> odd_elements = v[1::2]
>>> odd_elements
array([1, 3, 5, 7, 9])




3) Create a new array in backwards ordering from v
Ans:
>>>import numpy as np
>>>v=np.arange(5)
>>> rv=v[::-1]
>>> rv
array([9, 8, 7, 6, 5, 4, 3, 2, 1, 0])



4) What will be the output of the following code:

   a = np.array([1, 2, 3, 4, 5])
   b = a[1:4]    #######  array([1, 2, 3, 4, 5])
   b[0] = 200   #######  array([200,   3,   4])
   print(a[1])   ####### 200
>>> a
array([  1, 200,   3,   4,   5])




5) Create a two dimensional array called "m".
Ans:import numpy as np
>>> m=np.arange(10).reshape(2,5)
>>> m.ndim
2
>>> m
array([[0, 1, 2, 3, 4],
       [5, 6, 7, 8, 9]])

6) Create a new array from m, in which the elements of each row are in reverse order.

Ans:

import numpy as np
>>> m=np.arange(10).reshape(2,5)
>>> m.ndim
2
>>> m
array([[0, 1, 2, 3, 4],

       [5, 6, 7, 8, 9]])>>> m[::,::-1]

array([[4, 3, 2, 1, 0],

       [9, 8, 7, 6, 5]])

7) Another one, where the rows are in reverse order.

Ans:import numpy as np

>>> m=np.arange(10).reshape(2,5)
>>> m.ndim
2
>>> m
array([[0, 1, 2, 3, 4],
       [5, 6, 7, 8, 9]])
>>>>>> m[::-1]
array([[5, 6, 7, 8, 9],
       [0, 1, 2, 3, 4]])




8) Create an array from m, where columns and rows are in reverse order.

Ans:

import numpy as np

>>> m=np.arange(10).reshape(2,5)
>>> m.ndim
2
>>> m
array([[0, 1, 2, 3, 4],
       [5, 6, 7, 8, 9]])

>>> m[::-1,::-1]

array([[9, 8, 7, 6, 5],

       [4, 3, 2, 1, 0]])

9) Cut of the first and last row and the first and last column?

Ans:

import numpy as np

>>> m=np.arange(10).reshape(2,5)
>>> m.ndim
2
>>> m
array([[0, 1, 2, 3, 4],
       [5, 6, 7, 8, 9]])

>>> m[1:-1,1:-1]

array([], shape=(0, 3), dtype=int64)