def ReadFileIntoList(F):
    # This reads file F, which must already be open, into list L and returns L
    L = []
    for entry in F:
        num = int(entry)
        print num
        L.append(num)
    return L

def Average(L):
    # returns the average of the numbers in L
    if len(L) == 0:
        return 0.0
    sum = 0.0
    for value in L:
        sum = sum + value
    return sum/len(L)

def WriteListIntoFile(L):
    F = open("MyData.txt", "w")
    for value in L:
        F.write("%d\n" % value)
    F.close()
    
def main():
    try:
        F= open("MyData.txt", "r")
        L = ReadFileIntoList(F)
        F.close()
    except:
        L = []
    avg = Average(L)
    print "The average of the values in this file is %.2f" % avg
    L.sort()
    WriteListIntoFile(L)

main()