反射是什么，what why how

反射也叫内省，就是让对象自己告诉我们它都有什么方法

https://docs.python.org/3/library/functions.html?hight=hasattr#hasattr

1.hasattr(obj, attr): 这个方法用于检查obj（对象）是否有一个名为attr的值的属性，放回一个bool值

2.getattr(obj, attr): 调用这个方法将返回obj中名为attr值得属性的值

3.setattr(obj, attr, val): 调用这个方法将给obj的名为attr的值的属性赋值为val

s = 'coop'

s.upper()

'COOP'

isinstance(s,str)  # 检查实例

True

hasattr(s,'upper')  # 检查字符串是否有这个属性

True

class People:
    def eat(self):
        print('eat apple')

    def drink(self):
        print('drink water')

    def code(self):
        print('code python')

p = People()

p.eat()

eat apple

p.eat

<bound method People.eat of <__main__.People object at 0x000001AFCD677E80>>

hasattr(p,'eat')

True

hasattr(p,'code')

True

getattr(p,'code')

<bound method People.code of <__main__.People object at 0x000001AFCD677E80>>

code123 = getattr(p,'code')

print(code123)

<bound method People.code of <__main__.People object at 0x000001AFCD677E80>>

code123()

code python

setattr(p,'sleep','sleeper')

p.sleep

'sleeper'