Code Snippet

#  Purpose: Example: 'sentinel-controlled' while loop
#   Calculates average score of a class

# initialization phase
totalScore = 0     # sum of scores
numberScores = 0   # number of scores entered

# processing phase
score = input( "Enter score, (Enter -9 to end): " )   # get one score
score = int( score )   # convert string to an integer

while score != -9: # -9 is used as a sentinel ( a lookout or sentry value )
    totalScore = totalScore + score
    numberScores = numberScores + 1
    score = input( "Enter score, (Enter -9 to end): " )  
    score = int( score )
   
# termination phase
if numberScores != 0: # division by zero would be a run-time error
   average = float( totalScore ) / numberScores
   print ("Class average is", average)
else:
   print ("No scores were entered")

#http://www.annedawson.net/Python3Programs.txt
                    

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