将 Python 输入限制为 int

Question

如何使代码将用户的输入限制为整数。现在的代码工作得很好，但我希望它不是在输入字符串时给我一个错误，它只会成为一个例外。

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

input(( 将始终返回一个字符串。因此，您可以编写如下所示的帮助程序函数：

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

类似的助手可能会input_float，等等。

毫无疑问，如果你

需要的话，有一个具有更多花里胡哨的Python包。

Answer 2

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 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!')