1.必选参数、2.默认参数、3.可变参数、4.命名关键字参数、5.关键字参数
2.默认参数: def enroll(name, gender, age=6, city='Beijing'):
3.可变参数: def enroll(name, gender, *args):
4.命名关键字参数: def enroll(name, gender, *, age, city):
5.关键字参数 def enroll(name, gender, **kw):