Python 異常處理 - BMI 計算器

Question

我正在 python 中編寫一個 BMI 計算器，並想添加異常處理。 我創建了兩個函數 1. 一個高度轉換器，根據用戶的輸入將高度轉換為英尺或米，以及一個重量轉換器，根據輸入將用戶的體重轉換為公斤或磅。 當用戶輸入錯誤的輸入時，def height_converter(h) 和 weight_converter(w) 函數不會重新啟動，這與下面的代碼不同，它只詢問體重和高度。 另外，BMI變量返回錯誤，我不知道該怎么辦了

# 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，您只會在用戶輸入錯誤輸入時返回轉換后的值。 在 Python 中，縮進決定了語句屬於哪個代碼塊。 您需要將 return 語句放在與 while True 相同的縮進級別：這將它放在 while 循環之外，並且它基本上會在你們中的一個人休息后發生。

height_converter function 也有類似的問題。

此外，您僅在其中一個函數中引發 ValueError ，並且由於您在 except 塊中捕獲它們，因此它們不會傳播到調用者。

這段代碼的異常處理似乎增加了不必要的復雜性。 僅僅為了讓下一行代碼做一些不同的事情而引發 ValueError 是矯枉過正和令人困惑的。 這是一個更簡單的 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

未捕獲的異常沿調用堆棧向上傳播，直到它們被 except 塊捕獲。 如果它們沒有被捕獲，它們會導致解釋器停止程序並通常打印堆棧跟蹤。 如果此代碼導致異常，它們將被調用者中的異常處理程序捕獲。 如果您在此 function 中抓住它們，它們將永遠無法彌補調用者的損失。

Answer 2

測試您的代碼，在轉換函數中，代碼塊末尾的返回操作實際上並未被執行，因為它在邏輯上位於代碼塊的縮進中。 因此，您實際上是在向調用這些函數的語句返回“無”。

考慮到這一點，以下是您的代碼，其中進行了一些調整，以從體重和身高轉換函數返回轉換后的值。

# 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")

我應用了蠻力方法來確保返回值。 或者，您可以將 function 塊中的最后一個返回改進為只有一個返回，但我只是想避免在提供快速調整時可能出現的 scope 問題。

這產生了以下示例結果。

@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

試試看。