class BalanceError(Exception): 
    pass


class Customer:
    def __init__(self, name, balance):
        if balance < 0 :
            raise BalanceError("Balance has to be non-negative!")
        else:
            self.name, self.balance = name, balance

# Use try-except to catch errors
try:
    cust = Customer("Larry Torres", -100)
except BalanceError:
    cust = Customer("Larry Torres", 0)