check whether a user input is integer. If not, repeat again

Question

This is my current attempt

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?? "))

I've tried to repalce the == with is, but both return the following error

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

What should I do here?