user input validation for python

Question

I have a very simple question that I can't seem to find the answer to and am very new to python. I need to check a users input to see if the user has entered one of four operations. The operation are '^', '&', '|', and 'q' for quit. The user will be prompt again if they dont enter a valid operation so a while loop is needed, is there a way to test for all the operations in a single line? here is the code I have so far

    operation = input("enter an operation to be used\n")
    print('operation chosen:', operation)
    error = ("please enter |, &, ^, or q" )
    while operation != '&' 
    print(error)

Answer 1

This setup will only accept inputs that are in (^&|q) the loop will cycle until user inputs of of those choices, the beginning initializes operation to a value not in the list to start the loop.

operation = 'x'
while operation not in ('^&|q'):
    operation = input('Enter operation from "^%|q": ')
print('Operation chosen: {}'.format(operation))

 Enter operation from "^%|q": a Enter operation from "^%|q": s Enter operation from "^%|q": d Enter operation from "^%|q": ^ Operation chosen: ^ 

This route will do the same and prompt the user with a Invalid message, although this route requires a input before the loop to initialize operation

operation = input('Enter operation from "^&|q": ')
while operation not in ('^&|q'):
    operation = input('Invalid entry. Please choose from "^%|q": ')
print('Operation chosen: {}'.format(operation))

Answer 2

You can store all valid operations in an array and check the input against that array; correct input should break the loop, an incorrect input should raise the error and loop again.

Sample code below

allowd_operations= ['|','&','^', 'q' ]
operation = ''

while True:
    operation = input("enter an operation to be used\n")
    if operation in allowd_operations:
        # correct input
        break

    print('operation chosen:', operation)
    error = ("please enter |, &, ^, or q" )
    print(error)

Answer 3

Welcome to your Python journey. Here's a way to test user input with recursion and a function, which is helpful for larger projects, and those where some of these variables can change:

def checkinput(userinput):
    if userinput in ('|^&q'):
        return userinput
    else:
        loopinputline = input("please enter |, &, ^, or q\n" )
        return checkinput(loopinputline)


operation = str(input("enter an operation to be used\n"))
finalinput = checkinput(operation)
print('operation chosen:', finalinput)

Answer 4

list1=['^','&','|','q']
operation = raw_input('Enter operation from "^&|q": ')
while operation not in list1:
    operation = raw_input('Invalid entry. Please choose from "^&|q": ')
print(operation)

as per the question asked the user has to enter only one option. for answer by @cash_the stampede , if the user enters '^&' still it is accepting as the right answer, which should not be the case. so the above is just small correction.