Question

如何使代码将用户输入限制为整数。现在的代码工作正常，但我希望它在输入String时不会给我一个错误，它只会产生异常。

def miles_to_km():
        miles=eval(input('Amount of miles: '))
        result= float(miles*1.609344)
        print(miles, 'Miles are equivalent to ', result, 'Kilometers')
        print('----------------------------------------------------------------')
def km_to_miles():
        km=eval(input('Amount of kilometers: '))
        result= float(km*0.62137119)
        print(km, 'Kilometers are equivalent to ', result, 'Miles')
        print('----------------------------------------------------------------')
def pounds_to_kg():
        pounds=eval(input('Amount of pounds: '))
        result=float(pounds/2.2046226218)
        print(pounds, 'Pounds are equivalent to ', result, 'Kilograms')
        print('----------------------------------------------------------------')
def kg_to_pounds():
        kg=eval(input('Amount of kilograms: '))
        result=float(kg*2.2046226218)
        print(kg, 'Kilograms are equivalent to ', result, 'Pounds')
        print('----------------------------------------------------------------')
def C_to_F():
    temp=eval(input('Temperature in Celsius: '))
    result= float((temp*1.8)+32)
    print(temp, '°C are equivalent to ', result, '°F')
    print('----------------------------------------------------------------')
def F_to_C():
    temp=eval(input('Temperature in Fahrenheit '))
    result= float((temp-32)/1.8)
    print(temp, '°F are equivalent to ', result, '°C')
    print('----------------------------------------------------------------')
def mph_to_kph():
        mph=eval(input('Amount of Miles per hour: '))
        result= float(mph*1.609344)
        print(mph, 'Miles/Hour are equivalent to ', result, 'Kilometers/Hour')
        print('----------------------------------------------------------------')
def kph_to_mph():
        kph=eval(input('Amount of Kiometers per hour: '))
        result= float(kph*0.62137119)
        print(kph, 'Kilometers/Hour are equivalent to ', result, 'Miles/Hour')
        print('----------------------------------------------------------------')
def exit_function():
    print('Thanks for using the conversion program.')
    print('----------------------------------------------------------------')
    import sys
    sys.exit()


def menu():
    print('----------------------------------------------------------------')
    print('Welcome to the unit conversion program. Please select an option.')
    print('1. Miles to Kilometers')
    print('2. Kilometers to miles')
    print('3. Pounds to Kilograms')
    print('4. Kilograms to Pounds')
    print('5. Celsius to Fahrenheit')
    print('6. Fahrenheit to Celsius')
    print('7. Miles/hour to Kilometers/hour')
    print('8. Kilometers/hour to Miles/Hour')
    print('9. Exit')

screen=True

while screen:
    menu()
    choice=eval(input('Enter option: '))
    if choice==1:
        miles_to_km()
    elif choice==2:
        km_to_miles()
    elif choice==3:
        pounds_to_kg()
    elif choice==4:
        kg_to_pounds()
    elif choice==5:
        C_to_F()
    elif choice==6:
        F_to_C()
    elif choice==7:
        mph_to_kph()
    elif choice==8:
        kph_to_mph()
    elif choice==9:
        exit_function()
    else:
        print('Try a number between 1 and 9!')

Answer 1

您可以使用try语句转换输入。

while True:
    menu()
    choice = input('Enter option: ')
    try:
        choice = int(choice)
    except ValueError:
        print('invaild choice.')
        print('Try a number between 1 and 9!')
        continue
    if choice==1:
        miles_to_km()
    elif choice==2:
        km_to_miles()
    elif choice==3:
        pounds_to_kg()
    elif choice==4:
        kg_to_pounds()
    elif choice==5:
        C_to_F()
    elif choice==6:
        F_to_C()
    elif choice==7:
        mph_to_kph()
    elif choice==8:
        kph_to_mph()
    elif choice==9:
        exit_function()
    else:
        print('Try a number between 1 and 9!')

Answer 2

input（）将始终返回一个字符串。所以你可以编写一个这样的辅助函数：

def input_int(message):
    while True:
        try:
            number = int(input(message))
            return number
        except ValueError:
            print('Invalid number string, try again')
            continue

类似的帮助者可以输入_float等

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Answer 3

while screen:
    menu()
while True:
       try:

    choice=eval(input('Enter option: '))
    if choice==1:
        miles_to_km()
    elif choice==2:
        km_to_miles()
    elif choice==3:
        pounds_to_kg()
    elif choice==4:
        kg_to_pounds()
    elif choice==5:
        C_to_F()
    elif choice==6:
        F_to_C()
    elif choice==7:
        mph_to_kph()
    elif choice==8:
        kph_to_mph()
    elif choice==9:
        exit_function()
    else:
        print('Try a number between 1 and 9!')

将python输入限制为int

3 个答案: