浅谈python中的getattr函数 hasattr函数
hasattr(object, name)
作用：判断对象object是否包含名为name的特性（hasattr是通过调用getattr(ojbect, name)是否抛出异常来实现的）。
示例：
>>> hasattr(list, 'append') True >>> hasattr(list, 'add') False
getattr(object,name,default):
作用：返回object的名称为name的属性的属性值，如果属性name存在，则直接返回其属性值；如果属性name不存在，则触发AttribetError异常或当可选参数default定义时返回default值。
这个方法最主要的作用是实现反射机制。也就是说可以通过字符串获取方法实例。这样，你就可以把一个类可能要调用的方法放在配置文件里，在需要的时候动态加载。
下面我们使用小例子来说明它们的用法：
import func_file #自定义python模块
cs=input('请输入要访问的URL：')
if cs=='loggin':
func_file.loggin()
if cs =='home':
func_file.home()
if cs =='':
pass#以下省略当我定义一个自定义模块，去调用其中的方法的时候，使用if去判断时，如果模块内用很多方法，会大大影响开发的效率，代码冗余差，显然这是不可取的。下面我们使用hasattr()函数来实现我们的需求：
示例如下：
import func_file #自定义python模块，需事先存在
def run():
while True:
cs=input('请输入要访问的URL：')
#hasattr利用字符串的形式去对象（模块）中操作（寻找）成员
if hasattr(func_file,cs): #判断用户输入的URL是否在func_file模块中
func=getattr(func_file,cs) #有则将func_file模块下的cs函数赋值
func() #等同于执行func_file模块下的cs函数
else:
print('404')#定义错误页面
run()我们导入一个自定义模块后，gatattr可以根据输入的内容动态加载，利用hasattr()函数来判断用户输入的是否存在，不存在则调用自定义方法。
是不是感觉和我们打开网址URL很类似啊！
上一个示例有一个问题，在实际情况中，我们的功能函数可能存放在很多模块中，每一个都需要单独导入，那我们可不可以利用getattr()函数去动态加载模块呢？当然可以啦！
请看示例：
def run():
while True:
cs=input('请输入：')
v,k=cs.split('/') #获得输入的模块和模块的方法
obj=__import__('lib.'+v,fromlist=True) #调用lib目录下的模块fromlist=True按路径连接的方式导入
if hasattr(obj,k):
f= getattr(obj,k)
f()
else:
print('404')
if __name__ == '__main__':
run()是不是感到getattr很强大啊。其实，getattr()就是实现python反射的一块积木，结合其它方法如setattr(),dir() 等，我们可以还可以做出很多有趣的事情。
以上这篇浅谈python中的getattr函数 hasattr函数就是小编分享给大家的全部内容了，希望能给大家一个参考，也希望大家多多支持脚本之家。
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