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

  import pandas as pd

  print ( '' )
  print ( 'series_test():' )
  print ( '  Demonstrate the use of Series in pandas.' )
#
#  Create a Series from a list.
#
  print ( '' )
  print ( '  Create a series:' )
  print ( '    river_lengths = pd.Series ( [ 6300, 6650, 6275, 6400 ] )' )

  river_lengths = pd.Series ( [ 6300, 6650, 6275, 6400 ] )
  print ( river_lengths )
  input ( 'RETURN')
#
#  Print
#
  print ( '' )
  print ( '  Print with a loop "for i in range ( 0, 4 ):"' )

  for i in range ( 0, 4 ):
    print ( river_lengths[i] )
  input ( 'RETURN')
#
#  Print with a generator.
#
  print ( '' )
  print ( '  Print with a generator "for length in river_lengths:"' )

  for length in river_lengths:
    print ( length )
  input ( 'RETURN')
#
#  The index is an integer array by default.
#
  print ( '' )
  print ( '  Print river_lengths.index:' )
  print ( river_lengths.index )
  input ( 'RETURN')
#
#  Specify a better index.
#
  print ( '' )
  print ( '  Specify river names as the index, and print river_lengths:' )
  print ( "    river_lengths = pd.Series ( [ 6300, 6650, 6275, 6400 ]," )
  print ( "      index = [ 'Yangtze', 'Nile', 'Mississippi', 'Amazon' ] )" )

  river_lengths = pd.Series ( [ 6300, 6650, 6275, 6400 ],
    index = [ 'Yangtze', 'Nile', 'Mississippi', 'Amazon' ] )
  print ( river_lengths )
  input ( 'RETURN')
#
#  Use the new index.
#
  print ( '' )
  print ( '  Use a river name to index a river length:' )
  print ( "  river_lengths['Nile'] = ", river_lengths['Nile'] )
  input ( 'RETURN')
#
#  Specify index, name and dtype.
#
  print ( '' )
  print ( '  Specify index, name and dtype.' )
  print ( "    river_lengths = pd.Series ( [ 6300, 6650, 6275, 6400 ]," )
  print ( "      index = [ 'Yangtze', 'Nile', 'Mississippi', 'Amazon' ]," )
  print ( "      name = 'Length (km)', dtype = float )" )

  river_lengths = pd.Series ( [6300, 6650, 6275, 6400 ],
    index = [ 'Yangtze', 'Nile', 'Mississippi', 'Amazon' ],
    name = 'Length (km)', dtype = float )

  print ( '' )
  print ( '  print river_lengths' )
  print ( river_lengths )
  print ( '' )
  print ( '  print river_lengths["Nile"]' )
  print ( river_lengths['Nile'] )
  print ( '' )
  print ( '  print river_lengths["Yangtze":"Mississippi"]' )
  print ( river_lengths['Yangtze':'Mississippi'] )
  input ( 'RETURN')
#
#  Filter the data.
#
  print ( '' )
  print ( '  Filter the data.' )
  print ( '  print ( river_lengths[river_lengths < 6500] ):' )
  print ( river_lengths[river_lengths < 6500] )
  input ( 'RETURN')
#
#  Convert to miles.
#
  river_lengths_miles = river_lengths * 0.621371
  river_lengths_miles.name = 'Length (miles)'
  print ( '' )
  print ( '  Make a new Series, "river_lengths_miles"' )
  print ( '    river_lengths_miles = river_lengths * 0.621371' )
  print ( '    river_lengths_miles.name = "Length (miles)"' )
  print ( river_lengths_miles )
  input ( 'RETURN')
#
#  Create two series from dicts.
#  Then create a third series by combining these two. 
#
  print ( '' )
  print ( '  Series for mass of astronomical bodies:' )
  print ( "    mass = pd.Series ( { " )
  print ( "        'Ganymede' : 1.482e23, " )
  print ( "        'Callisto' : 1.076323, " )
  print ( "        'Io'       : 8.932e22, " )
  print ( "        'Europa'   : 4.800e22, " )
  print ( "        'Moon'     : 7.342e22, " )
  print ( "        'Earth'    : 5.972e24 }," )
  print ( "        name = 'mass (kg)' )" )

  mass = pd.Series ( { \
    'Ganymede' : 1.482e23, \
    'Callisto' : 1.076323, \
    'Io'       : 8.932e22, \
    'Europa'   : 4.800e22, \
    'Moon'     : 7.342e22, \
    'Earth'    : 5.972e24 },
    name = 'mass (kg)' )
  print ( mass )

  print ( '' )
  print ( '  Series for radius of astronomical bodies:' )
  print ( "    radius = pd.Series ( { " )
  print ( "      'Ganymede' : 2.634e6, " )
  print ( "      'Io'       : 1.822e6, " )
  print ( "      'Moon'     : 1.737e6, " )
  print ( "      'Earth'    : 6.371e6 }," )
  print ( "    name = 'radius (m)' )" )

  radius = pd.Series ( { \
    'Ganymede' : 2.634e6, \
    'Io'       : 1.822e6, \
    'Moon'     : 1.737e6, \
    'Earth'    : 6.371e6 },
    name = 'radius (m)' )
  print ( radius )
  input ( 'RETURN')
#
#  Create new series.
#
  print ( '' )
  print ( '  Create new series "gravity = G * mass / radius**2"' )

  from scipy.constants import G
  gravity = G * mass / radius**2
  gravity.name = 'surface gravity m/s**2'
  gravity.index.name = 'Body'
  print ( '' )
  print ( gravity )
  print ( '' )
  print ( '  gravity.isnull() checks for NaN values.' )
  print ( gravity.isnull() )
  print ( '' )
  print ( '  gravity = gravity.dropna() drops NaN entries.' )
  gravity = gravity.dropna()
  print ( gravity )
#
#  Extract values into numpy array.
#
  print ( '' )
  print ( '  gravity_array = gravity.values creates numpy array.' )
  gravity_array = gravity.values
  print ( gravity_array )

  return

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