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

  import pandas as pd

  print ( '' )
  print ( 'dataframe_test():' )
  print ( '  Demonstrate the use of Dataframes in pandas.' )
#
#  Create a DataFrame from a dictionary.
#
  print ( '' )
  print ( '  Create a DataFrame from a dictionary.' )
  print ( "    moon_data = { " )
  print ( "      'mass'   : [ 1.482e23,   1.076e23, 8.932e23,  4.800e22,  7.342e22 ], " )
  print ( "      'radius' : [ 2.634e6,    None,     1.822e6,   None,      1.737e6  ], " )
  print ( "      'parent' : [ 'Jupiter', 'Jupiter', 'Jupiter', 'Jupiter', 'Earth'  ] }" )
  print ( "    moon_index = [ 'Ganymede', 'Callisto', 'Io', 'Europa', 'Moon' ]" )
  print ( "    moon_df = pd.DataFrame ( moon_data, index = moon_index )" )

  moon_data = { \
    'mass'   : [ 1.482e23,   1.076e23, 8.932e23,  4.800e22,  7.342e22 ], \
    'radius' : [ 2.634e6,    None,     1.822e6,   None,      1.737e6  ], \
    'parent' : [ 'Jupiter', 'Jupiter', 'Jupiter', 'Jupiter', 'Earth'  ] }

  moon_index = [ 'Ganymede', 'Callisto', 'Io', 'Europa', 'Moon' ]

  moon_df = pd.DataFrame ( moon_data, index = moon_index )

  input ( 'RETURN' )
#
#  Print the information.
#
  print ( '' )
  print ( '  print ( moon_df ):' )
  print ( moon_df )
  input ( 'RETURN' )
#
#  Use loc() to see a value.
#
  print ( '' )
  print ( '  Print a row using loc[]' )
  print ( '    print ( moon_df.loc["Europa"] )' )
  print ( moon_df.loc['Europa'] )
  input ( 'RETURN' )

  print ( '' )
  print ( '  Print a column using loc[]' )
  print ( '    print ( moon_df.loc[:,"mass"] )' )
  print ( moon_df.loc[:,'mass'] )
  input ( 'RETURN' )

  print ( '' )
  print ( '  Print an entry (a cell) using loc[]' )
  print ( '    print ( moon_df.loc["Europa","mass" )' )
  print ( moon_df.loc['Europa','mass'] )
  input ( 'RETURN' )
#
#  Use loc() to change a value.
#
  print ( '' )
  print ( '  Change an entry using loc[]' )
  print ( '    print ( moon_df.loc["Callisto","radius" )' )
  print ( moon_df.loc['Callisto','radius'] )
  input ( "RETURN" )

  moon_df.loc['Callisto','radius'] = 2410300
  print ( '' )
  print ( '    moon_df.loc["Callisto","radius"] = 2410300' )
  print ( moon_df )
  input ( 'RETURN' )
#
#  Select a portion of the DataFrame
#
  print ( '' )
  print ( '  Select a portion of the DataFrame using loc[]:' )
  print ( '' )
  print ( '  moon_df.loc[:,["mass","radius"]]' )
  print ( moon_df.loc[:,['mass','radius']] )
  print ( '' )
  print ( '  moon_df.loc[["Moon","Europa"],"parent"]' )
  print ( moon_df.loc[['Moon','Europa'],'parent'] )
  print ( '' )
  print ( '  moon_df.loc[moon_df.parent=="Jupiter","radius"]' )
  print ( moon_df.loc[moon_df.parent=='Jupiter','radius'] )
  input ( 'RETURN' )
#
#  Use iloc() to see a value using numeric index.
#
  print ( '' )
  print ( '  Print a row using iloc[] and numeric index' )
  print ( '    print ( moon_df.iloc[3] )' )
  print ( moon_df.iloc[3] )

  print ( '' )
  print ( '  Print a column using iloc[]' )
  print ( '    print ( moon_df.iloc[:,0] )' )
  print ( moon_df.iloc[:,0] )

  print ( '' )
  print ( '  Print an entry (a cell) using iloc[]' )
  print ( '    print ( moon_df.iloc[3,0] )' )
  print ( moon_df.iloc[3,0] )
  input ( 'RETURN' )

  return

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