类的反射

一、概念

　　Python中反射是作用于类中的方法和属性，通过字符串映射或修改程序运行时的状态、属性、方法。

二、反射方法

　　2.1、hasattr(obj,name_str)

　　判断一个对象obj中是否有对应的name_str字符串的属性或者方法　　

class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:")    # 用户输入的形式来判断是否存在该方法

print(hasattr(p, choice))


# 输出

>>:sport
True

# 输入其他方法
>>:walk
False

# 测试属性
>>:name
True

>>:age
False

　　

　　2.1、getattr(obj,name_str)

　　根据字符串name_str获取obj对象中的对应方法的内存地址或者对应属性的值　

class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:")

print(hasattr(p, choice))
print(getattr(p, choice))

# 输出
>>:sport
True
<bound method Person.sport of <__main__.Person object at 0x000001AA97F2D9E8>>   # 获取了该方法的内存地址

　　有了方法的内存地址，我们调用直接加()就行了

class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:").strip()

print(hasattr(p, choice))
func = getattr(p, choice)
func('football')

# 输出
>>:sport
True
Bigberg is good at football

　　

　　2.3 setattr(x,y,v)

　　作用：给obj对象添加一个新属性或者新方法，setattr(x, 'y', v) is equivalent to ``x.y = v''

　　1. 新增一个方法　　

def hobby(self, favour):    # 在类 外又定义了一个函数hobby
    print('%s is fond of %s' % (self.name, favour))


class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:").strip()


setattr(p, choice, hobby)   #参数分别为 对象，方法/属性名， 函数名
p.hobby(p, 'football')       # 调用时要传入一个self参数，所有我们要把对象p穿进去
func = getattr(p, choice)  # 上面的调用方法可以，但不是很清晰
func(p, 'football')

# 输出
>>:hobby
Bigberg is fond of football
Bigberg is fond of football

　　2. 新增一个属性　

def hobby(self, favour):
    print('%s is fond of %s' % (self.name, favour))


class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:").strip()


setattr(p, choice, 22)   # 新增一个属性age = 22

attr = getattr(p, choice)
print(attr)

# 输出
>>:age
22

　　

　　2.4 delattr()

　　删除obj对象中的属性或者方法，delattr(x, 'y') is equivalent to ``del x.y''　

class Person(object):

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

    def sport(self, item):
        print("%s is good at %s" % (self.name, item))

p = Person('Bigberg')

choice = input(">>:").strip()

# 删除属性
delattr(p, choice)
print(p.name)

>>:name
Traceback (most recent call last):
  File "G:/python/untitled/study6/反射.py", line 21, in <module>
    print(p.name)
AttributeError: 'Person' object has no attribute 'name'

# 删除方法

delattr(p, choice)
p.sport('football')

>>:sport
Traceback (most recent call last):
  File "G:/python/untitled/study6/反射.py", line 21, in <module>
    delattr(p, choice)
AttributeError: spor

　　

 三、事例

class Dog(object):
    def __init__(self, name):
        self.name = name

    def eat(self, food):
        print("{0} is eating...{1}".format(self.name, food))


d = Dog("hashiky")
choice = input(">>>:").strip()

if hasattr(d, choice):  # 判断d对象中存在属性和方法
    name_value = getattr(d, choice)  # 获取属性值
    print(name_value)
    setattr(d, choice, "hong")  # 修改属性值
    print(getattr(d, choice))  # 重新获取属性的值
else:
    setattr(d, choice, None)  # 设置不存在的属性值为None
    v = getattr(d, choice)
    print(v)