limitar la entrada de python a int

¿Cómo puedo hacer que el código limite la entrada del usuario a números enteros? El código ahora funciona a la perfección, pero quiero que en lugar de darme un error cuando ingrese una cadena, solo hará una excepción.

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!') 

input () siempre devolverá una cadena. Así que podrías escribir una función de ayuda como esta:

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

Un ayudante análogo podría input_float, etc.

No hay duda de que un paquete de Python con más campanas y silbidos, si los necesita.

Usted podría convertir la entrada con la statement de try .

 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!') 
 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!')