gistfile1.py

def get_account(name):
    if name == "Irek": return 1, None
    elif name == "John": return 2, None
    elif name == "Alex": return 3, None
    elif name == "Nick": return 1, None
    else: return None, "No account associated with name '%s'" % name

def get_balance(account):
    if account == 1: return 1000000, None
    elif account == 2: return 75000, None
    else: return None, "No balance associated with account #%s" % account

def get_loan(balance):
    if balance > 200000: return balance, None
    else: return None, "Insufficient funds for loan, current balance is %s" % balance


def bind(mval, mf):
    value = mval[0]
    error = mval[1]

    if not error:
        return mf(value)
    else:
        return mval

def unit(value):
    return value, None


# business logic
def get_loan2(name):
    return bind(get_account(name), lambda account:
           bind(get_balance(account), lambda balance:
           bind(get_loan(balance), lambda loan:
                unit(loan)