isinstance、issubclass、反射

一、isinstance、issubclass

# isinstance(obj, cls)
    检查obj是否是cls的对象

class A(object):pass
a = A()
print(isinstance(a, A))  # True


# issubclass(sub, super)
    检查sub是否是super的派生类

class A(object):pass
class B(A):pass
print(issubclass(B, A))  # True

二、反射

用字符串形式的名字去操作对象相关的属性（python中一切皆对象）

hasattr、getattr

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

    def func(self):
        print("func")

a = A("pd")

# 反射对象的属性
if hasattr(a, "name"):
    ret = getattr(a, "name")
    print(ret)

# 反射对象的方法
if hasattr(a, "func"):
    getattr(a, "func")()  # func

class A(object):
    name = "pd"

    @classmethod
    def func(self):
        print("func")

# 反射类的属性
if hasattr(A, "name"):
    ret = getattr(A, "name")  # pd
    print(ret)

# 反射类的方法
if hasattr(A, "func"):
    getattr(A, "func")()  # func

# demo.py
name = "pd"

def func():
    print("func in demo")

#########################

# test.py
import demo

# 反射模块的属性
if hasattr(demo, "name"):
    ret = getattr(demo, "name")
    print(ret)
    
#反 射模块的方法
if hasattr(demo, "func"):
    getattr(demo, "func")()

import sys

name = "pd"

def func():
    print("func")

#反射本模块中的属性
if hasattr(sys.modules["__main__"], "name"):
    ret = getattr(sys.modules["__main__"], "name")
    print(ret)  # pd

#反射本模块中的函数
if hasattr(sys.modules["__main__"], "func"):
    getattr(sys.modules["__main__"], "func")()  # func

setattr：设置/修改变量
delattr：删除一个变量

class A(object):
    name = "盲僧"

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

a = A("pd")

setattr(a, "name", "诺手")
setattr(A, "name", "德玛")
print(a.name)  # 诺手
print(A.name)  # 德玛

delattr(a, "name")
print(a.name)  # 德玛  对象的name属性已被删除，就找类的

delattr(A, "name")
print(A.name)  # 报错  类中的name也被删除，找不到了