class Pair:
    def __init__(self,x,y):
        self.x = x
        self.y = y

    def __str__(self):
        return "(%s,%s)"%(self.x,self.y)

    def __repr__(self):
        return "Pair(%s,%s)"%(self.x,self.y)

p = Pair(2,5)
print(p)
print("p is {0!r}".format(p))

_formats = {
    "ymd":"{d.year}-{d.month}-{d.day}",
    "mdy":"{d.month}/{d.day}/{d.year}",
    "dmy":"{d.day}/{d.month}/{d.year}"
}

class Date:
    def __init__(self,year,month,day):
        self.year = year
        self.month = month
        self.day = day

    def __format__(self,code):
        if code == "":
            code = "ymd"
        fmt = _formats[code]
        return fmt.format(d = self)

d = Date(2018,9,26)
print(format(d))
print(format(d,"dmy"))
print(format(d,"mdy"))

from socket import socket,AF_INET,SOCK_STREAM

class LazyConnection:
    
    def __init__(self,address,family = AF_INET, type = SOCK_STREAM):
        self.address = address
        self.family = family
        self.type = type
        self.sock = None

    def __enter__(self):
        if self.sock is not None:
            raise RuntimeError("Already connected")
        self.sock = socket(self.family,self.type)
        self.sock.connect(self.address)
        return self.sock

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.sock.close()
        self.sock = None

conn = LazyConnection("www.baidu.com")

with conn as s:
    s.send(b'hahhahah')

class Date:
    __slots__ = ["year","month","day"]

    def __init__(self,year,month,day):
        self.year = year
        self.month = month
        self.day = day

class A:
    def __init__(self):
        self._name = "jiaojianglong"
        self.age = 24

    def _internal_method(self):
        print("i am a internal method")


a = A()
print(a._name) #jiaojianglong

class B:
    def __init__(self):
        self.__name = "jiaojianglong"

b = B()
# print(b.__name)#AttributeError: 'B' object has no attribute '__name'
print(b._B__name)#jiaojianglong

class C(B):
    def __init__(self):
        super().__init__()

c = C()
print(c._B__name)#jiaojianglong

class Person:
    def __init__(self,first_name):
        self.first_name = first_name

    @property
    def first_name(self):
        return self._first_name

    @first_name.setter
    def first_name(self,value):
        if not isinstance(value,str):
            raise TypeError("Excepted a string")
        self._first_name = value



p = Person("jiao")
print(p.first_name)

class A:
    def spam(self):
        print("A.spam")

class B(A):
    def spam(self):
        print("B.spam")
        super().spam()

b = B().spam()#B.spam,A.spam

print(B.__mro__)#(<class '__main__.B'>, <class '__main__.A'>, <class 'object'>)

class Integer():

    def __init__(self,name):
        self.name = name

    def __get__(self, instance, owner):
        if instance is None:
            return self
        else:
            return instance.__dict__[self.name]

    def __set__(self, instance, value):
        if not isinstance(value,int):
            raise TypeError("Expected an int")
        instance.__dict__[self.name] = value

    def __delete__(self, instance):
        del instance.__dict__[self.name]


class Point:
    x = Integer("x")
    y = Integer("y")

    def __init__(self,x,y):
        self.x = x
        self.y = y

p = Point(2,3)
print(p.x)#2
p.y = 5
print(p.y)#5
# p.x = "a"#TypeError: Expected an int
print(Point.x)#<__main__.Integer object at 0x00000141E2ABB5F8>

class Point:

    def __init__(self,x,y):
        self.x = Integer("x")
        self.y = Integer("y")
        self.x = x
        self.y = y

p = Point(2,"c")
print(p.x)#2
print(p.y)#c

class Typed:
    def __init__(self,name,expected_type):
        self.name = name
        self.expected_type = expected_type


    def __get__(self, instance, owner):
        if instance is None:
            return self
        else:
            return instance.__dict__[self.name]

    def __set__(self, instance, value):
        if not isinstance(value,self.expected_type):
            raise TypeError("Expected %s"%self.expected_type)
        instance.__dict__[self.name] = value

    def __delete__(self, instance):
        del instance.__dict__[self.name]

def typeassert(**kwargs):
    def decorate(cls):
        for name,expected_type in kwargs.items():
            setattr(cls,name,Typed(name,expected_type))
        return cls
    return decorate

@typeassert(name=str,shares = int,price=float)
class Stock:
    def __init__(self,name,shares,price):
        self.name = name
        self.shares = shares
        self.price = price