如何修复这个Python BMI计算器？

Question

这是我在python中编写的BMI计算器

print('BMI calculator V1')

name = str(input("What's your name?"))
weight = int(input("Your weight in Kilograms"))
height = float(input("Your height in Metres"))

def function(w, h):    #function here is the bmi calculator
     bmi = w / h ** 2
     return("Your BMI is " + str(bmi))

bmi_user = function(weight, height)  
print(bmi_user)  

if bmi_user < 18:
     print(name + "," + "you are underweight")
elif bmi_user > 25:
     print(name + "," + "you are overweight")
else:
     print(name + "," + "you are normal")

它在运行代码时显示以下错误

第15行，如果float（bmi_user）<18： ValueError：无法将字符串转换为float：

Answer 1

错误消息很明确：您无法在字符串和double之间进行比较。

看看你的函数返回的内容：一个字符串。

def function(w, h):    #function here is the bmi calculator
     bmi = w / h ** 2
     return("Your BMI is " + str(bmi))

bmi_user = function(weight, height) 

你会做得更好：

def bmi_calculator(w, h):    
     return w / h ** 2 

Answer 2

通过不从计算中返回字符串来修复它。您应该将此How to debug small programs (#1)读取并按照它来调试您的代码。

print('BMI calculator V1')

name = str(input("What's your name?"))
weight = int(input("Your weight in Kilograms"))
height = float(input("Your height in Metres"))

def calcBmi(w, h):    # function here is the bmi calculator
     bmi = w / h ** 2
     return bmi        # return a float, not a string

bmi_user = calcBmi(weight, height)  # now a float
print(f'Your BMI is: {bmi_user:.2f}')   # your output message

if bmi_user < 18:
     print(name + "," + "you are underweight")
elif bmi_user > 25:
     print(name + "," + "you are overweight")
else:
     print(name + "," + "you are normal")

function不是一个非常好的名字，我改为calcBmi。

Answer 3

你的函数def函数（w，h）：返回一个字符串，如下所示。

return("Your BMI is " + str(bmi))

这不能与您在下面的语句中指定的整数进行比较。

if bmi_user < 18:

以下行也将是一个错误

elif bmi_user > 25:

如下更改您的功能，它将工作

def function(w, h):    #function here is the bmi calculator
    bmi = w / h ** 2
    return bmi