#! /usr/bin/env python3
#
def python05 ( ):

  import matplotlib.pyplot as plt
  import numpy as np

  print ( '' )
  print ( 'python05():' )
  print ( '  Exercises for loops.' )
#
#  Loop to evaluate the triangular numbers.
#
  print ( '' )
  print ( '  Evaluate triangular numbers for 0 <= n < 11.')
  print ( '' )
  for n in range ( 0, 11 ):
    print ( '  t(', n, ') = ', n * ( n + 1 ) / 2 )
  print ( '' )
  print ( '  Repeat calculation, using // for integer division.')
  print ( '' )
  for n in range ( 0, 11 ):
    print ( '  t(', n, ') = ', n * ( n + 1 ) // 2 )
#
#  Code which includes nonindented statements before and after loop.
#
  print ( '' )
  print ( '  Non-indented statements before and after loop.')
  print ( '' )
  s = 0
  print ( '  S starts out at ', s )
  for n in range ( 1, 11 ):
    t = n * ( n + 1 ) // 2
    s = s + t
    print ( '  t(', n, ') = ', t )
  print ( '  Sum of triangular numbers is ', s )
#
#  The range statement returns a list of loop indices.
#
  print ( '' )
  print ( '  The range statement returns a list of loop indices.')
  print ( '' )
  r0 = list ( range ( 10 ) )
  print ( '  range ( 10 ) = ', r0 )
  r1 = list ( range ( 0, 10 ) )
  print ( '  range ( 0, 10 ) = ', r1 )
  r2 = list ( range ( 10, 10 ) )  # Oops
  print ( '  range ( 10, 10 ) = ', r2 )
  r3 = list ( range ( 10, 0 ) )   # Oops
  print ( '  range ( 10, 0 ) = ', r3 )
  r4 = list ( range ( 10, 0, -1 ) )
  print ( '  range ( 10, 0, -1 ) = ', r4 )
  r5 = list ( range ( 0, 10, 2 ) )
  print ( '  range ( 0, 10, 2 ) = ', r5 )
#
#  Using a list instead of range():
#
  print ( '' )
  print ( '  We can use a list instead of range().' )
  print ( '' )
  UScoins = [ 1, 5, 10, 25, 50, 100 ]
  print ( '  UScoins = ', UScoins )
  sum = 0
  for coin in UScoins:
    sum = sum + coin
  print ( '  The sum of a collection of US coins is ', sum )

  print ( '' )
  friends = [ 'Alice', 'Bob', 'Carol', 'David' ]
  print ( '  friends = ', friends )
  for friend in friends:
    print ( '  My friend', friend, 'has a name of length ', len ( friend ) )  

  print ( '' )
  patient0 = [ 'Robert Baratheon', 235.4, 73, False ] 
  print ( '  patient0 = ', patient0 )
  patient1 = [ 'Arya Stark', 134.7, 68, True ]
  print ( '  patient1 = ', patient1 )
  patients = [ patient0, patient1 ]
  print ( '  patients = ', patients )
  for name, weight, height, vax in patients:
    print ( name, ' weighs ', weight, 'lbs and is ', height, 'inches tall.' )
#
#  Nested loop.
#
  print ( '' )
  print ( '  A nested loop allows us to process matrix entries.' )
  print ( '' )
  m = 4
  n = 3
  A = np.random.rand ( m, n )
  print ( '  A = ', A )
  average = 0.0
  for i in range ( 0, m ):
    for j in range ( 0, n ):
      average = average + A[i,j]
  average = average / m / n
  print ( '' )
  print ( '  average matrix entry is ', average )
#
#  While loop for triangular numbers.
#
  print ( '' )
  print ( '  While loop for triangular numbers.' )
  print ( '' )
  n = 1
  while ( n * ( n + 1 ) // 2 < 1000 ):
    n = n + 1
  print ( ' 1000 <= t(', n,') = ', n * ( n + 1 ) // 2 )

  return

if ( __name__ == "__main__" ):
  python05 ( )