Lecture 10 --- Exercises
========================

Solutions to the problems below must be sent to Submitty for grading.
A separate file must submitted for each problem.  Since the disscusion
of loops and lists is so important and because you do not have lab
next week, this set of exercises is somewhat longer than normal.
Solutions must be submitted by 4 pm on Fridday, October 7.

#. Submit a text file showing the output of the following code:

   ::

      L1 = [ 1, 5, [5, 2], 'hello' ]
      L2 = L1
      L3 = L1.copy()
      L2.append( 4 )
      L1.append( 3 )
      print(L1)
      print(L2)
      print(L3)

#. Submit a text file showing the output of the following code

   ::

      def head_and_tail(L):
          from_back = L.pop()
          from_front = L.pop(0)
          L.append(from_front)
          L.insert(0,from_back)

      L1 = [ [1, 2], 3 ]
      L3 = L1.copy()
      L2 = L1
      L2[-1] = 5
      L2.insert(1,6)
      head_and_tail(L1)

      print(L1[0], L1[-1], len(L1))
      print(L2[0], L2[-1], len(L2))
      print(L3[0], L3[-1], len(L3))

#. The solution to this problem and the two that follow should start
   with the assignment

   ::

      co2_levels = [ 320.03, 322.16, 328.07, 333.91, 341.47, \
                     348.92, 357.29, 363.77, 371.51, 382.47, 392.95 ]

   Write a Python program that prints the number of values that are greater
   than the average of the list.  For this you may use Python's
   ``sum`` and ``len`` functions and you must use a ``for`` loop.  Do
   NOT use a ``range,`` however, and do not use indexing.

   Your output should simply be:

   ::

      Average: 351.14
      Num above average: 5

#. Suppose we discovered that the measurement of CO2 values was
   uniformly too low by a small fraction ``p``.  Write a function that
   increases each value in ``co2_levels`` by the fraction ``p``.  (In
   other words if ``x`` is the value before the increase then
   ``x*(1+p)`` is the value after.)  For this problem you need to use
   a ``range`, :func:`len` and indexing.  Start by asking the user for the
   percentage.  Output the first and last values of the revised list.
   Your program should end with the lines

   ::

      print('First: {:.2f}'.format(co2_levels[0]))
      print('Last: {:.2f}'.format(co2_levels[-1]))
   
   Here is an example of running your program:

   ::

      Enter the fraction: 0.03
      First: 329.63
      Last: 404.74

#. Write a function called ``is_increasing`` that returns ``True`` if
   the values in the list it is passed are in increasing order and
   ``False`` otherwise.  Use a ``for`` loop and indexing to accomplish
   this.  Test the function with the following main code:

   ::

      print('co2_levels is increasing: {}'.format(is_increasing(co2_levels)))
      test_L1 = [ 15, 12, 19, 27, 45 ]
      print('test_L1 is increasing: {}'.format(is_increasing(test_L1)))
      test_L2 = [ 'arc', 'circle', 'diameter', 'radius', 'volume', 'area' ]
      print('test_L2 is increasing: {}'.format(is_increasing(test_L2)))
      test_L3 = [ 11, 21, 19, 27, 28, 23, 31, 45 ]
      print('test_L3 is increasing: {}'.format(is_increasing(test_L3)))

   These should be the only :func:`print` function calls in the code
   you submit.