Calculate single, double, triple factorials

# Type your text herefrom math import gamma, sqrt
from math import *

def factorial(x):
    return gamma(x + 1)

def double_factorial(n):
    result = 1
    while n > 1:
        result *= n
        n -= 2
    return result

def triple_factorial(n):
    result = 1
    while n > 1:
        result *= n
        n -= 3
    return result

while True:
    expr = input("Enter n!, n!!, or n!!! \n(or 'quit' to exit): ")

    if expr.lower() in ("quit", "exit"):
        print("Goodbye!")
        break
      
    bangs = 0
    while expr.endswith("!"):
        bangs += 1
        expr = expr[:-1]

    if bangs not in (1, 2, 3):
        print("Use 1, 2, or 3 factorials.")
        continue

    try:
        x = eval(expr)
    except:
        print("Invalid number or expression.")
        continue

    if bangs == 1:
        value = factorial(x)
    else:
        if x < 0 or int(x) != x:
            print("Double/triple factorial needs a non-negative integer.")
            continue
        n = int(x)
        value = double_factorial(n) if bangs == 2 else triple_factorial(n)

    print("Result:", value)