学习Python中遇到的问题，求指教！

# -*- coding: UTF-8 -*-
class Person:
    '''Represents a person'''
    population=0
    def _init_(self,name):
        self.name=name
        print '初始化参数 %s'%self.name
        Person.population+=1
    def _del_(self):
        '''I am dying'''
        print '%s says Bye'%self.name
        Person.population-=1
        if population==0:
            print ' I am the last one'
        else:
            print 'There are still %d people leftl'%Person.population
    def sayHi(self):
        '''Greeting by the people.

        Really,that's all it does.'''
        print 'Hi,My name is %s'%self.name
    def howMany(self):
        '''print the current population'''
        if population==1:
            print 'I am the only one person here'
        else:
            print 'We have %d persons here'%Person.population
print '测试开始！'
toby=Person('toby Huang')
toby.sayHi()
toby.howMany()

jimmy=Person('jimmy Huang')
jimmy.sayHi()
jimmy.howMany()

toby.sayHi()
toby.howMany()

依照教程学习Python过程中，自己输入上述代码后出现这样的错误！保存为ObjVarTest.Py文件。在IDLE的shell主界面中报错如下：

>>> import ObjVarTest.py
测试开始！

Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    import ObjVarTest.py
  File "ObjVarTest.py", line 29, in <module>
    toby=Person('toby Huang') 
 
TypeError: this constructor takes no arguments

我的Python版本是2.7.5。这个问题困扰我许久，但有找不到问题所在!希望有知道的朋友能够不吝赐教！ python shell class _init_方法
[解决办法]
呵呵 细心很重要