教教孩子怎么改写函数吧

参考以下代码（可完成上述功能），改写为基于函数BMI（h,w）实现上述功能。
height,weight=eval(input())
bmi=weight/(height*height)
who,dom="",""
if bmi<18.5:
who,dom="偏瘦","偏瘦"
elif 18.5<=bmi<24:
who,dom="正常","正常"
elif 24<=bmi<25:
who,dom="正常","偏胖"
elif 25<=bmi<28:
who,dom="偏胖","偏胖"
elif 28<=bmi<30:
who,dom="偏胖","肥胖"
else:
who,dom="肥胖","肥胖"
print("BMI={:.2f}，指标为：国际{}-国内{}".format(bmi,who,dom))