#!/usr/bin/env python
# coding=utf-8
class Account(object):
def __init__(self, number):
self.number = number
self.balance = 0
def deposit(self, amount):
assert amount > 0
self.balance += balance
def withdraw(self, amount):
assert amount > 0
if amount <= self.balance:
self.balance -= amount
else:
print "balance is not enough."
if __name__ == "__main__":
a = Account(1000)
a.deposit(-10)