python中出現'>=' not supported between instances of 'str' and 'int'錯誤

提示錯誤為： TypeError: '>=' not supported between instances of 'str' and 'int'
 因為 input 接收到的都是字符串類型，解決方案是轉變字符類型。 
score=int(input ("請輸入你的成績:"))
if score >= 90:
    print('優秀')
elif score < 90 and score>=80:
    print('良好')
elif score < 80 and score>=60:
    print('及格')
else:
    print('不及格')