python04():
  Exercises for lists.

  Create a list of colleges

['Carlow', 'Chatham', 'CMU', 'Duquesne', 'University of Pittsburgh']
Chatham
['Chatham', 'CMU', 'Duquesne']
University of Pittsburgh
  Number of colleges in list is  5

  Replace, modify, append, remove entries.

['Carlow', 'Chatham', 'CMU', 'Robert Morris', 'University of Pittsburgh']
['Carlow', 'Chatham', 'CMU', 'Robert Morris University', 'University of Pittsburgh']
['Carlow', 'Chatham', 'CMU', 'Robert Morris University', 'University of Pittsburgh', 'Point Park']
['Carlow', 'CMU', 'Robert Morris University', 'University of Pittsburgh', 'Point Park']

  Remove an entry by index.

['Carlow', 'CMU', 'Robert Morris University', 'University of Pittsburgh', 'Point Park']
  value = colleges.pop(1) =  CMU
['Carlow', 'Robert Morris University', 'University of Pittsburgh', 'Point Park']
  value = colleges.pop(1) =  Robert Morris University
['Carlow', 'University of Pittsburgh', 'Point Park']
  value = colleges.pop(0) =  Carlow
['University of Pittsburgh', 'Point Park']

  The len() function reports the length of a list:

  len(colleges) =  2
  len ( [ 10, 20, 30, 40 ] ) =  4

  A list can contain a mixture of types:

  patient0 =  ['Robert Baratheon', 235.4, 73, False]
  patient1 =  ['Arya Stark', 134.7, 68, True]

  The + sign will concatenate lists.

  odd =  [1, 3, 5, 7, 9]
  prime =  [2, 3, 5, 7]
  oddplusprime =  [1, 3, 5, 7, 9, 2, 3, 5, 7]
  oddandprime =  [2, 3, 5, 7]

  A list can contain lists:

  patientpluspatient =  ['Robert Baratheon', 235.4, 73, False, 'Arya Stark', 134.7, 68, True]
patients= [['Robert Baratheon', 235.4, 73, False], ['Arya Stark', 134.7, 68, True]]
patients[1]= ['Arya Stark', 134.7, 68, True]
patients[0][1]= 235.4

  Use append to add one more list to a list of lists:

[['Robert Baratheon', 235.4, 73, False], ['Arya Stark', 134.7, 68, True], ['Tyrion Lannister', 140.5, 50, True]]

  A list name is only a pointer.
  A=B makes a new pointer, but not a new set of values.

prime =  [3, 5, 7]
odds =  [3, 5, 7]

  A=B.copy() makes a new pointer and a new set of values.

prime =  [3, 5, 7]
odds =  [1, 3, 5, 7, 9]