哨兵循环：文件循环求平均值

 1 def main():
 2     fileName=input("What file are the numbers in?")
 3     infile=open(fileName,‘r‘)
 4     sum=0
 5     count=0
 6     for line in infile:
 7         sum=sum+eval(line)
 8         count=count+1
 9     print("\nThe average of the numbers is",sum/count)
10 main()

1 line=infile.readline()
2 while line!=""
3     #处理每一行
4     line=infile.readline()

1 for xStr in line.split(",")
2     sum=sum+eval(xStr)
3     count=count+1