检查用户输入是否为整数。如果没有，请再次重复

Question

这是我目前的尝试

quantity = int(input("How many do you want?? "))
while (quantity < 1 or isinstance(quantity, int) == False):
    print("Error! Please enter a valid quantity value :)")
    quantity = int(input("How many do you want?? "))

我尝试将 == 替换为 ，但两者都返回以下错误

ValueError: invalid literal for int() with base 10: 'a'

我该怎么办？