python初学者编程过程中遇到问题

用python编写了个Person类：
''
Created on 2014年9月19日

@author: Administrator
'''

class Person:

def __init__(self,name,age,salary=0,job=None):
        self.name=name
        self.age=age
        self.salary=salary
        self.job=job

def lastName(self):
    return self.name.split()[-1]

def giveRaise(self,percent):
    self.salary *= (1.0+percent)

if __name__ == '__main__' :
        bob = Person('tom',22,8000,'software')
        sue =  Person('jack',23,10000,'hardware')
        print(bob.name,sue.salary)

        print(bob.name.split()[-1])
        bob.salary*=1.10
        print(bob.salary)

 但bob = Person('tom',22,8000,'software')
   sue =  Person('jack',23,10000,'hardware')这里报错，错误信息：

Undefined variable: Person
class Person Found at: com.onewaveinc.cas.person_start

应该是Person 这个名称与com.onewaveinc.cas.person_start冲突，把Person改个其它名再运行一下