#  MeanvalueList.py  Copyright (c) Kari Laitinen

#  http://www.naturalprogramming.com

#  2006-05-27  File created.
#  2022-12-16  Converted to Python 3.

#  This program stores the given numbers in a Python list
#  before calculating their mean value. Python does not
#  have the conventional fixed-size arrays that are common
#  in other programming languages. Lists are dynamic arrays
#  that can grow as is necessary.

#  In this program list method append() is used to add new
#  items to the end of the list. In program Reverse.py
#  the same operation is carried out with the + operator.

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" )

list_of_numbers  =  []

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 )

   except :

      keyboard_input_is_numerical  =  False



sum_of_numbers  =  0.0

for  number_in_list  in  list_of_numbers :

   sum_of_numbers  =  sum_of_numbers  +  number_in_list


mean_value  =  0.0

if  len( list_of_numbers )  >  0  :

   mean_value  =  sum_of_numbers / len( list_of_numbers )


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