Learning immediately: https://edu.csdn.net/course/play/26755/340142?utm_source=blogtoedu
format definition string: {} is achieved primarily by
class person:
def_init_(self):
self.age =20
self.name='bill'
person = person()
s='my name is {p.name}.my age is {p.age}'
print(s.format(p=person))
