一、isinstance和issubclass
class Foo:
pass
class Son(Foo):
pass
s = Son()
#判断一个对象是不是这个类的对象,传两个参数（对象，类）
# print(isinstance(s,Son))
# print(isinstance(s,Foo))
# print(type(s) is Son)
# print(type(s) is Foo)
#判断一个类是不是另一类的子类，传两个参数(子类，父类)
print(issubclass(Son,Foo))
print(issubclass(Son,object))
print(issubclass(Foo,object))
print(issubclass(int,object))
二、反射
python面向对象中的反射：通过字符串的形式操作对象相关的属性。python中的一切事物都是对象（都可以使用反射）
四个方法:hasattr(),getattr(),setattr(),delattr()
1.对象中
__author__ = 'ctz'
class Foo:
def __init__(self,name,age):
self.name=name
self.age=age
def fun(self):
print("...........ctz")
f=Foo("ctz",21)
print(hasattr(f,"name"))
print(hasattr(f,"age"))
print(hasattr(f,"fun"))
print(getattr(f,"name"))
print(getattr(f,"age"))
print(getattr(f,"fun"))
fu=getattr(f,"fun")
fu()
print("".center(50,"-"))
setattr(f,"name","egon")
setattr(f,"age",73)
print(f.name,f.age)
print("--------------------")
delattr(f,"name")
print(f.name)
True
True
True
ctz
21
<bound method Foo.fun of <__main__.Foo object at 0x00000000023F9DD8>>
...........ctz
--------------------------------------------------
egon 73
--------------------
Traceback (most recent call last):
File "G:/test/week6/day27/反射1 对象.py", line 32, in <module>
print(f.name)
AttributeError: 'Foo' object has no attribute 'name'
2.类中
__author__ = 'Administrator'
class Foo:
f=123
@staticmethod
def static():
print("static......")
@classmethod
def clas(cls):
print(cls.f,"class.............")
print(hasattr(Foo,"f"))
print(hasattr(Foo,"static"))
print(hasattr(Foo,"clas"))
if hasattr(Foo,"f"):
print(getattr(Foo,"f"))
print(getattr(Foo,"static"))
print(getattr(Foo,"clas"))
s=getattr(Foo,"static")
s()
c=getattr(Foo,"clas")
c()
True
True
True
123
<function Foo.static at 0x000000000241B9D8>
<bound method Foo.clas of <class '__main__.Foo'>>
static......
123 class.............
3.模块
import my_module
# print(hasattr(my_module,'test'))
# # func_test = getattr(my_module,'test')
# # func_test()
# getattr(my_module,'test')()
#import其他模块应用反射
from my_module import test
def demo1():
print('demo1')
import sys
print(__name__) #'__main__'
print(sys.modules)
#'__main__': <module '__main__' from 'D:/Python代码文件存放目录/S6/day26/6反射3.py'>
module_obj =sys.modules[__name__] #sys.modules['__main__']
# module_obj : <module '__main__' from 'D:/Python代码文件存放目录/S6/day26/6反射3.py'>
print(module_obj)
print(hasattr(module_obj,'demo1'))
getattr(module_obj,'demo1')()
#在本模块中应用反射
__author__ = 'Administrator'
import aa
print(hasattr(aa,"bb"))
g=getattr(aa,"bb")
g()
def Demo():
print("本模块自己的反射")
import sys
print(sys.modules)
module=sys.modules[__name__]
if hasattr(module,"Demo"):
d=getattr(module,"Demo")
d()
def bb():
print("bbbbb")
#aa
二、内置方法:
__str__和__repr__
改变对象的字符串显示__str__,__repr__
自定制格式化字符串__format__
class Foo:
def __init__(self,name):
self.name = name
def __str__(self):
return '%s obj info in str'%self.name
def __repr__(self):
return 'obj info in repr'
f = Foo('egon')
# print(f)
print('%s'%f)
print('%r'%f)
print(repr(f)) # f.__repr__()
print(str(f))
#当打印一个对象的时候，如果实现了str，打印中的返回值
#当str没有被实现的时候，就会调用repr方法
#但是当你用字符串格式化的时候 %s和%r会分别去调用__str__和__repr__
#不管是在字符串格式化的时候还是在打印对象的时候，repr方法都可以作为str方法的替补
#但反之不行
#用于友好的表示对象。如果str和repr方法你只能实现一个：先实现repr
__del__
析构方法，当对象在内存中被释放时，自动触发执行。
注：此方法一般无须定义，因为Python是一门高级语言，程序员在使用时无需关心内存的分配和释放，因为此工作都是交给Python解释器来执行，所以，析构函数的调用是由解释器在进行垃圾回收时自动触发执行的。
__author__ = 'Administrator'
class Foo:
def __del__(self):
print("执行我来")
f = Foo()
print(123)
print(123)
del f
print(123)
print(123)
print(123)
item系列
__getitem__\__setitem__\__delitem__
class Foo:
def __init__(self):
self.name = 'egon'
self.age = 73
def __getitem__(self, item):
return self.__dict__[item]
def __setitem__(self, key, value):
# print(key,value)
self.__dict__[key] = value
def __delitem__(self, key):
del self.__dict__[key]
f = Foo()
# f['name'] = 'alex'
# del f['name']
# print(f.name)
f1 = Foo()
print(f == f1)
# print(f[0])
# print(f[1])
# print(f[2])
单例模式
class Singleton:
def __new__(cls, *args, **kw):
if not hasattr(cls, '_instance'):
orig = super(Singleton, cls)
cls._instance = orig.__new__(cls, *args, **kw)
return cls._instance
one = Singleton()
two = Singleton()
two.a = 3
print(one.a)
# 3
# one和two完全相同,可以用id(), ==, is检测
print(id(one))
# 29097904
print(id(two))
# 29097904
print(one == two)
# True
print(one is two)
单例模式
__call__
对象后面加括号，触发执行。
注：构造方法的执行是由创建对象触发的，即：对象 = 类名() ；而对于 __call__ 方法的执行是由对象后加括号触发的，即：对象() 或者 类()()
class Foo:
def __init__(self):
pass
def __call__(self, *args, **kwargs):
print('__call__')
obj = Foo() # 执行 __init__
obj() # 执行 __call__
__len__
class A:
def __init__(self):
self.a = 1
self.b = 2
def __len__(self):
return len(self.__dict__)
a = A()
print(len(a))
# class Foo:
# # def __len__(self):
# # return len(self.__dict__)
# def __hash__(self):
# print('my hash func')
# return hash(self.name)
# f = Foo()
# # print(len(f))
# f.name = 'egon'
# # print(len(f))
# print(hash(f))
__hash__
class A:
def __init__(self):
self.a = 1
self.b = 2
def __hash__(self):
return hash(str(self.a)+str(self.b))
a = A()
print(hash(a))
__eq__
class A:
def __init__(self):
self.a = 1
self.b = 2
def __eq__(self,obj):
if self.a == obj.a and self.b == obj.b:
return True
a = A()
b = A()
print(a == b)
纸牌游戏
class FranchDeck:
ranks = [str(n) for n in range(2,11)] + list('JQKA')
suits = ['红心','方板','梅花','黑桃']
def __init__(self):
self._cards = [Card(rank,suit) for rank in FranchDeck.ranks
for suit in FranchDeck.suits]
def __len__(self):
return len(self._cards)
def __getitem__(self, item):
return self._cards[item]
deck = FranchDeck()
print(deck[0])
from random import choice
print(choice(deck))
print(choice(deck))
纸牌游戏
纸牌游戏2
class FranchDeck:
ranks = [str(n) for n in range(2,11)] + list('JQKA')
suits = ['红心','方板','梅花','黑桃']
def __init__(self):
self._cards = [Card(rank,suit) for rank in FranchDeck.ranks
for suit in FranchDeck.suits]
def __len__(self):
return len(self._cards)
def __getitem__(self, item):
return self._cards[item]
def __setitem__(self, key, value):
self._cards[key] = value
deck = FranchDeck()
print(deck[0])
from random import choice
print(choice(deck))
print(choice(deck))
from random import shuffle
shuffle(deck)
print(deck[:5])
纸牌游戏2
面试题
class Person:
def __init__(self,name,age,sex):
self.name = name
self.age = age
self.sex = sex
def __hash__(self):
return hash(self.name+self.sex)
def __eq__(self, other):
if self.name == other.name and self.sex == other.sex:return True
p_lst = []
for i in range(84):
p_lst.append(Person('egon',i,'male'))
print(p_lst)
print(set(p_lst))
一道面试题