如何确保用户在python中输入一组给定的数字

Question

I am trying to make a program in python in which a user can only input 1, 2 or 3. I tried this method but it does not work.`

x = input("Enter your Choice: ")    
while (x!=1 or x!=2 or x!=3):
    x = input("Enter your Choice: ")

Using this method it continually asks for input even if 1, 2 or 3 or any other number is keyed in. Can anybody tell please tell me why this does not work and also suggest a correct way to enter these three numbers.

Answer 1

This is what we call a logic error .

The line should be like this:

while (x!=1 and x!=2 and x!=3):

That is, change the or to and .

To handle any input and give out the error if it's not 1,2 or 3, do this:

x = raw_input("Enter your Choice: ")    
while (x!='1' and x!='2' and x!='3'):
    x = raw_input("Enter your Choice: ")

Answer 2

Try:

def userchoicevalidator(): 
    x = input("Please Enter Your Choice: ") 
    while x not in list('123'): 
        x = input("Please Enter Your Choice: ")

the reason that raw_input wasn't working for you is because it has been deprecated in python 3. input is in python 3. Also note that this returns a string, not an integer, which is why your booleans checks were failing unexpectedly