#  MeanvalueFunction.py  Copyright (c) Kari Laitinen

#  http://www.naturalprogramming.com

#  2006-05-23  File created.
#  2022-12-16  Converted to Python 3.

#  This program stores the given numbers in a list.
#  The corresponding Java/C++/C# programs (e.g. MeanvalueMethod.java)
#  use an array to store the given numbers. This program uses
#  a list because lists are standard Python data structures for
#  storing a set of similar data items.

#  The following two functions use a variable which tells how
#  many numbers are stored in the list. This is redundant information
#  as a list always 'knows' the number of its list items.
#  In file pythonfilesextra\MeanvalueFunctionAlternative.py
#  you find another version of this program where this variable is
#  not in use.

def ask_numbers_to_list( list_of_numbers ) :

   number_of_given_numbers  =  0

   keyboard_input_is_numerical  =  True

   while  keyboard_input_is_numerical ==  True  :

      try :

         print(  "   Enter a number: ", end="" )
         number_from_keyboard  =  float( input() )
         list_of_numbers.append( number_from_keyboard )
         number_of_given_numbers +=  1

      except :

         keyboard_input_is_numerical  =  False

   return  number_of_given_numbers


def calculate_mean_value( list_of_numbers,
                          number_of_numbers_in_list ) :

   calculated_mean_value  =  0
   sum_of_numbers         =  0

   for  number_index  in  range( number_of_numbers_in_list ) :

      sum_of_numbers  =  sum_of_numbers  +  \
                         list_of_numbers[ number_index ]


   if  number_of_numbers_in_list  >  0 :

      calculated_mean_value  =  sum_of_numbers / number_of_numbers_in_list


   return  calculated_mean_value


#  The main program begins.

list_of_numbers  =  []

print( "\n This program calculates the mean value of"  \
      "\n the numbers you enter from the keyboard."   \
      "\n The program stops when you enter a letter.\n" )

number_of_numbers_read  =  ask_numbers_to_list( list_of_numbers )

mean_value  =  calculate_mean_value( list_of_numbers,
                                     number_of_numbers_read )

print( "\n The mean value is: %f"  %  mean_value )