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)