Определение переменной класса в функции (python 3.6)

#                                             CLASS
class bankcard:
 
    # Create attributes
    def __init__(self, cardnumber, cardtype, owner, validdate, moneyvalue, cardcurrency):
        self.cardnumber = cardnumber
        self.cardtype = cardtype
        self.owner = owner
        self.validdate = validdate
        self.moneyvalue = moneyvalue
        self.cardcurrency = cardcurrency
 
    # Check card balance
    def balance(self):
        return "Card money value = %s" % self.moneyvalue
 
    # Check card type
    def type(self):
        pass
 
    # Check owner information
    def info(self):
        pass
 
    # Check valid date of card
    def date(self):
        pass
 
    # Check card currency
    def currency(self):
        pass
 
    # Check card number
    def number(self):
        pass

from BankCard import bankcard
 
# тут работает
first = bankcard("1042 5123 3523 0001", "Visa", "Surname Name", "10/20", 100000, "USD")
print("Out",first.balance())
 
#                                             MAIN
def main():
 
    # тут не работает
    first = bankcard("1042 5123 3523 0001", "Visa", "Surname Name", "10/20", 100000, "USD")
    print("In",first.balance())