list.remove(x): x not in list on a random number list

I am getting list.remove(x) error so what am I doing here is that, am using this program to generate random numbers without duplicates from a set range and removing the number as the number has been called but somehow I am getting not in the list message even though the random has been called from the list.

import random
def checkPizza(numOfPizza):
    pizzaD = []
    allowed_val = list(range(0,M+1))
    if numOfPizza == 2:
        allowed_val = allowed_val
        while True:
            allowed_val = allowed_val
            alpha = random.choice(allowed_val)
            beta = random.choice(allowed_val)
            if alpha != beta:
                allowed_val.remove(alpha)
                allowed_val.remove(beta)
                pizzaD.append(alpha)
                pizzaD.append(beta)
                break

I guess if any one can help me in this case ... i know it is kind of noob but I`m new to programming so