cs50p/problems/pset0/einstein/einstein.py

c = 300000000


def compute_energy():
    mass = None
    while not isinstance(mass, int):
        input_string = input("Enter a mass:\t\t")
        try:
            mass = int(input_string)
        except (ValueError, TypeError):
            mass = None
    print(mass*(c**2))


if __name__ == "__main__":
    compute_energy()