Objective Questions
-------------------
.. A mininum of 8 questions here (along with answers)
1. Given the array, ``A = array([12, 15, 18, 21])``, how do we access
the element ``18``?
Answer: ``A[2]``
#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
accessed by ``A[1]``
Answer: ``15``
#. Given the array, ``A = array([12, 15, 18, 21])``, what element is
accessed by ``A[-3]``?
Answer: ``15``
#. Given the array, ``A = array([12, 15, 18, 21])``, how do you change
the element ``15`` to ``51``?
Answer: ``A[1] = 51``
#. Given the array, ``A = array([12, 15, 18, 21])``, what is ``A``
after the execution of the statement ``A[3] = 24``?
Answer: ``array([12, 15, 18, 24])``
#. Given the array, ``A = array([12, 15, 18, 21])``, what is the
result of the statement, ``A[4] = 24``?
Answer: IndexError: index out of bounds
#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do we
access the element ``18``?
Answer: ``A[0, 0]``
#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
result of ``B[1]``?
Answer: ``array([18, 21])``
#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
result of ``B[1, 1]``?
Answer: ``21``
#. Given the array, ``B = array([[12, 15], [18, 21]])``, what element
is accessed by ``B[-1, -2]``?
Answer: ``18``
#. Given the array, ``B = array([[12, 15], [18, 21]])``, how do you
change the element ``15`` to ``51``?
Answer: ``B[0, 1] = 51``
#. Given the array, ``B = array([[12, 15], [18, 21]])``, what is the
value of B, after executing, ``B[0] = 0``?
Answer: ``array([[0, 0], [18, 21]])``
#. Given the array,
::
B = array([[10, 11, 12, 13],
[20, 21, 22, 23],
[30, 31, 32, 33],
[40, 41, 42, 43]])
Obtain the elements, ``[[21, 22], [32, 32]]``
Answer: ``B[1:3, 1:3]``
#. Given the array,
::
B = array([[10, 11, 12, 13],
[20, 21, 22, 23],
[30, 31, 32, 33],
[40, 41, 42, 43]])
Obtain the elements, ``[[10, 13], [30, 33]]``
Answer: ``B[::2, ::3]``
#. What command is used to read an image file?
a. imshow
#. imread
#. imopen
#. open
Answer: ``imread``
#. If ``P`` is ``array([12, 13, 14, 15])`` then ``P.shape`` gives
``(4, 1)``. True or False?
Answer: False
Larger Questions
----------------
.. A minimum of 2 questions here (along with answers)
1. Given the array,
::
B = array([[10, 11, 12, 13],
[20, 21, 22, 23],
[30, 31, 32, 33],
[40, 41, 42, 43]])
Change the array to
::
B = array([[10, 11, 10, 11],
[20, 21, 20, 21],
[10, 11, 10, 11],
[20, 21, 20, 21]])
using slicing and striding.
Answer::
B[:2, 2:] = B[:2, :2]
B[2:, :2] = B[:2, :2]
B[2:, 2:] = B[:2, :2]
#. Find out how to display a grayscale image with proper colors. Hint,
use ``?`` on ``imshow``.
Answer: ``cmap=cm.gray``
#. From the image, ``tagore-einstein.png``,
a. show only the face of Einstein.
b. show only the face of Tagore.
Hint, use ``imread`` to read the image and ``imshow`` to show the
image. Use ``cm.gray`` as ``cmap`` to display the image properly.
Answer::
F = imread('tagore-einstein.png')
imshow(F[:210, 20:180], cmap=cm.gray)
F = imread('tagore-einstein.png')
imshow(F[30:300, 320:480], cmap=cm.gray)
.. #[Puneeth: This question contains answer to previous
.. question. Shouldn't be shown at the same time.]