【MOOC语言程序设计】分支结构-实例5
分支结构-实例5：身体质量指数BMI
基本知识点：
- 分支结构
单分支结构，if；二分支结构（有紧凑结构）if，else；多分支结构（注意包含关系&变量取值范围的覆盖）if，elif，else
- 异常处理
- 实例5：身体质量指数BMI
try:num = eval(input())print(num**2)except NameError: #标注异常类型后，仅响应异常；#异常类型名字等同于变量print()
#CalBMIv3.pyheight,weight = eval(input())bmi = weight/(height**2)print("BMI数值为：{:.2f}".format(bmi))who,nat = "","" #预定义变量who和nat类型为字符串，没有这行也可if bmi < 18.5:who,nat = "偏瘦","偏瘦"elif 18.5 <= bmi < 24:who,nat = "正常","正常"elif 24<=bmi <25:who,nat = "正常","偏胖"elif 25 <= bmi <28:who, nat = "偏胖","偏胖"elif 28 <= bmi <30:who,nat = "偏胖","肥胖"else:who,nat = "肥胖","肥胖"print("BMI指标为：国际{}，国内{}".format(who,nat))