Python 异常处理 - BMI 计算器

Question

我正在 python 中编写一个 BMI 计算器，并想添加异常处理。 我创建了两个函数 1. 一个高度转换器，根据用户的输入将高度转换为英尺或米，以及一个重量转换器，根据输入将用户的体重转换为公斤或磅。 当用户输入错误的输入时，def height_converter(h) 和 weight_converter(w) 函数不会重新启动，这与下面的代码不同，它只询问体重和高度。 另外，BMI变量返回错误，我不知道该怎么办了

# BMI CALCULATOR IN PYTHON
import os
from datetime import datetime
# define our clear function
def clear():
    # for windows
    if os.name == 'nt':
        os.system('cls')
    # for mac and linux(here, os.name is 'posix')
    else:
        _ = os.system('clear')
def weight_converter(w):
    while True:
        try:
            global converted
            converted = 0
            weight_unit = input("What is the weight unit Kgs or Lbs: ")
            if weight_unit.upper() == "KG":
                converted = w / 1
                print("weight in kg is: ", converted)
            elif weight_unit.upper() == "LBS":
                converted = w / 2.2
                print("weight in kg is: ", converted)
            else:
                raise ValueError(weight_unit)
            break
        except (ValueError, IOError, IndexError):
            print("ERROR")
            return converted
def height_converter(h):
    while True:
        try:
            height_unit = input("what is the height unit meters or feet: ")
            if height_unit.upper() == "METERS":
                converted = h / 1
                print("height in meters is: ", converted)
            elif height_unit.upper() == "FEET":
                converted = h / 3.281
                print("height in meters is: ", converted)
            break
        except(ValueError,IOError,IndexError):
            print("ERROR")
        return converted
while True:
    try:
        age = input("How old are you? ")
        age = int(age)

        weight = input("What is your weight: ")
        weight = float(weight)
        wconverted = weight_converter(weight)
      
        height = input("What is your height: ")
        height = float(height)
        hconverted = height_converter(height)
        break
    except ValueError:
        # os.system(clock_settime)
        print("No valid integer! Please try again ...")
        clear()
BMI = float(wconverted / (hconverted ** 2))
print("Your BMI is: ", BMI, "as of ", date) 
print("You are using a", os.name, "system")

Answer 1

在您的 weight_converter function 中，您只会在用户输入错误输入时返回转换后的值。 在 Python 中，缩进决定了语句属于哪个代码块。 您需要将 return 语句放在与 while True 相同的缩进级别：这将它放在 while 循环之外，并且它基本上会在你们中的一个人休息后发生。

height_converter function 也有类似的问题。

此外，您仅在其中一个函数中引发 ValueError ，并且由于您在 except 块中捕获它们，因此它们不会传播到调用者。

这段代码的异常处理似乎增加了不必要的复杂性。 仅仅为了让下一行代码做一些不同的事情而引发 ValueError 是矫枉过正和令人困惑的。 这是一个更简单的 weight_converter function 版本。

def weight_converter(w):
    while True:
        weight_unit = input("What is the weight unit Kgs or Lbs: ")
        if weight_unit.upper() == "KG":
            conversion = 1.0
            break
        elif weight_unit.upper() == "LBS":
            conversion = 2.2
            break
        else
            print("ERROR")
    converted = w / conversion
    print("weight in kg is: ", converted)
    return converted

未捕获的异常沿调用堆栈向上传播，直到它们被 except 块捕获。 如果它们没有被捕获，它们会导致解释器停止程序并通常打印堆栈跟踪。 如果此代码导致异常，它们将被调用者中的异常处理程序捕获。 如果您在此 function 中抓住它们，它们将永远无法弥补调用者的损失。

Answer 2

测试您的代码，在转换函数中，代码块末尾的返回操作实际上并未被执行，因为它在逻辑上位于代码块的缩进中。 因此，您实际上是在向调用这些函数的语句返回“无”。

考虑到这一点，以下是您的代码，其中进行了一些调整，以从体重和身高转换函数返回转换后的值。

# BMI CALCULATOR IN PYTHON
import os
from datetime import date     # FYI, I revised this a bit as well for the date
# define our clear function
def clear():
    # for windows
    if os.name == 'nt':
        os.system('cls')
    # for mac and linux(here, os.name is 'posix')
    else:
        _ = os.system('clear')
def weight_converter(w):
    while True:
        try:
            global converted
            converted = 0
            weight_unit = input("What is the weight unit Kgs or Lbs: ")
            if weight_unit.upper() == "KG":
                converted = w / 1
                print("weight in kg is: ", converted)
                return converted            # Made sure a decimal value was being returned
            elif weight_unit.upper() == "LBS":
                converted = w / 2.2
                print("weight in kg is: ", converted)
                return converted            # Same here
            else:
                raise ValueError(weight_unit)
            break
        except (ValueError, IOError, IndexError):
            print("ERROR")
            return 0.0
def height_converter(h):
    while True:
        try:
            height_unit = input("what is the height unit meters or feet: ")
            if height_unit.upper() == "METERS":
                converted = h / 1
                print("height in meters is: ", converted)
                return converted            # And here
            elif height_unit.upper() == "FEET":
                converted = h / 3.281
                print("height in meters is: ", converted)
                return converted            # And finally here
            break
        except(ValueError,IOError,IndexError):
            print("ERROR")
        return 1.0
while True:
    try:
        age = input("How old are you? ")
        age = int(age)

        weight = input("What is your weight: ")
        weight = float(weight)
        wconverted = weight_converter(weight)
      
        height = input("What is your height: ")
        height = float(height)
        hconverted = height_converter(height)
        break
    except ValueError:
        # os.system(clock_settime)
        print("No valid integer! Please try again ...")
        clear()
BMI = float(wconverted / (hconverted ** 2))
print("Your BMI is: ", BMI, "as of ", date.today())     # You had not defined the variable "date"
print("You are using a", os.name, "system")

我应用了蛮力方法来确保返回值。 或者，您可以将 function 块中的最后一个返回改进为只有一个返回，但我只是想避免在提供快速调整时可能出现的 scope 问题。

这产生了以下示例结果。

@Una:~/Python_Programs/BMI$ python3 Calculator.py 
How old are you? 66
What is your weight: 170
What is the weight unit Kgs or Lbs: lbs
weight in kg is:  77.27272727272727
What is your height: 5.83333
what is the height unit meters or feet: feet
height in meters is:  1.7779122218835721
Your BMI is:  24.445876294351564 as of  2022-09-06
You are using a posix system

试试看。