Python意外实参问题

#第六题
class Student:
def int(self,sno,name):
self.sno=sno
self.name=name
def str(self):
return '学号:'+self.sno+',姓名:'+self.name
if name=='main':
ls1=[23,56,12,37,28]
ls1.sort()
print('ls1升序排序的结果：',ls1)
ls1.sort(reverse=True)
print('ls1降序排序的结果：', ls1)
ls2= [Student('810101', '李晓明'), Student('1810100', '马红'), Student('1810102', '张刚')]
ls2.sort(key=lambda stu:stu.sno)
print('ls2按学号升序排序后的结果：')
for stu in ls2:
print(stu)
ls2.sort(key=lambda stu:stu.sno,reverse=True)
print('ls2按学号降序排列后的结果：')
for stu in ls2:
print(stu)

class Student:
    def __init__(self,sno,name):
        self.sno=sno
        self.name=name
    def str(self):
        return '学号:'+self.sno+',姓名:'+self.name
if __name__=='__main__':
    ls1=[23,56,12,37,28]
    ls1.sort()
    print('ls1升序排序的结果：',ls1)
    ls1.sort(reverse=True)
    print('ls1降序排序的结果：', ls1)
    ls2= [Student('810101', '李晓明'), Student('1810100', '马红'), Student('1810102', '张刚')]
    ls2.sort(key=lambda stu:stu.sno)
    print('ls2按学号升序排序后的结果：')
    for stu in ls2:
        print(stu.str())
    ls2.sort(key=lambda stu:stu.sno,reverse=True)
    print('ls2按学号降序排列后的结果：')
    for stu in ls2:
        print(stu.str())