Python程序：输入成绩，输出对应等级（各个成绩段所对应的等级事先提前定义）

score=float(input("Enter your score: "))
if score>=90 and score<=100:
    print("A")
elif score>=70 and score<90:
    print("B")
elif score>=60 and score<70:
    print("C")
elif score>=0 and score<60:
    print("D")
else:
    print("Invalid score")