Objective Questions

-------------------

.. A mininum of 8 questions here (along with answers)

1. An array in Python is the same as a Python list

   a. True

   #. False

Answer: False

2. ``x = array([1, 2, 3], [5, 6, 7])`` is a valid statement

   a. True

   #. False

Answer: False

3. What will be the output of the following code,

   ::

      x = array([[1, 2, 3], ['a', 2, 'c']])

      print x[0][0] + x[0][1] + x[0][2] 

   a. 6

   #. 123

   #. a2c

   #. Error as array takes only homogeneous elements

Answer: 123

4. What will be the output of the following code,

   ::

	x = [[1, 2, 3], [4.1, 4.2, 4.3], ['6','7',8]]

	y = array(x)

	print y[-1][-2] + y[-1][-1] + y[-2][0] + y[0][-2]

   a. 21.1

   #. 12.5

   #. 784.12

   #. Error as array takes only homogeneous elements

   .. 4.2 4.3 2 2

Answer: 784.12

5. What is the output of the following code,

   ::

      x = array([[1, 2, 3], ['a', 2, 'c']])

      identity(x.shape)

   a. Will create an identity matrix of shape (2, 3).

   #. ``identity()`` function takes an integer as argument and a tuple

      is passed.

   #. Will return, array([[1,0,1],[0,1,0]])

   #. Will return, array([[0,1,0],[0,1,0]])

Answer: ``identity()`` function takes an integer as argument and a

      	tuple is passed.

6. ``ones_like()`` function?

   (A) Returns an array of ones with the same shape and type as a

       given array.

   (B) Return a new array of given shape and type, filled with ones.

   Read the statements and answer,

   a. Only statement A is correct.

   #. Only statement B is correct.

   #. Both statement A and B are correct.

   #. Both statement A and B are incorrect.

Answer: Only statement A is correct.

7. ``zeros_like()`` function?

   (A) Return a new array of given shape and type, filled with zeros.

   (B) Returns an array of zeros with the same shape and type as a

       given array.

   Read the statements and answer,

   a. Only statement A is correct.

   #. Only statement B is correct.

   #. Both statement A and B are correct.

   #. Both statement A and B are incorrect.

Answer: Only statement B is correct.

8. What will be output of the following code snippet.

   ::

      x = linspace(1,10,10).reshape(5,2)

      print (x[-3]+x[-4]).sum()

   a. 10.0 

   #. 18.0

   #. 14.0

   #. 16.44

   #. Error

Answer: 18

Larger Questions

----------------

.. A minimum of 2 questions here (along with answers)

1. Write a python script to create a 15x15 array of equally spaced 225

   elements from 1 to 1000, add 5 to each of the diagonal elements and

   find the sum of all odd rows of the array. Say for example the

   array,

   ::

       x = array([[1, 2, 3],

		  [4, 5, 6],

		  [7, 8, 9]])

   will give answer 40 ((1+5) + 2 + 3 + 7 + 8 + (9+5)).

2. For any given array([a1, a2, a3, .. , an]) the Vandermonde matrix

    will be [[1, a1, a1**2, .. , a1**(n-1)], [1, a2, a2**2, .. ,

    a2**(n-1)], .. , [1, an, an**2, .. ,an**(n-1)]]. Write a python

    script to generate the Vandermonde matrix and find the determinant

    of the matrix for [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

    16, 17, 18, 19, 20].  [Hint: to find the determinant use the

    function ``det()`` from ``linalg`` module.]