入门 Python ，有一段脚本看不明白，望指教。谢谢！

def print_seat(seat):
for item in seat:
print "${}".format(item)
print "-"*15
total = get_seat_total(seat)
print "Total:${}".format(total)

def get_seat_total(seat):
total = 0
for dish in seat:
total = total+dish
return total

def main():
seats = [[19.95],[20.45+3.10],[7.00/2,2.10,21.45],[7.00/2,2.10,14.99]]

grand_total = 0
for seat in seats:
print_seat(seat)
grand_total = grand_total+get_seat_total(seat)
print "\n"
print "="*15
print "Grand total:$()".format(grand_total)

if __name__=="__main__":
main()


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搞不懂这段程序的流程，《Python入门经典》这本书上的例子。