#!/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)