Python hasattr, getattr, modules判断模块属性是否存在

hasattr菜鸟实例：

#!/usr/bin/python
# -*- coding: UTF-8 -*-
 
class Coordinate:
    x = 10
    y = -5
    z = 0
 
point1 = Coordinate() 
print(hasattr(point1,'x'))
print(hasattr(point1,'y'))
print(hasattr(point1,'z'))
print(hasattr(point1,'no'))  # 没有该属性

结果：

True
True
True
False

 

getattr菜鸟实例：

>>>class A(object):
...     bar = 1
... 
>>> a = A()
>>> getattr(a,'bar')        # 获取属性 bar 值
1
>>> getattr(a,'bar2')       # 属性 bar2 不存在，触发异常
Traceback (most recent call last):
  File "<stdin>",line 1,in <module>
AttributeError: 'A' object has no attribute 'bar2'
>>> getattr(a,'bar2',3)    # 属性 bar2 不存在，但设置了默认值
3
>>>

 

开源项目实例：

from sys import modules

# UserDB is the default auth_class
        authname = auth.UserDB                              #UserDB为类对象
 
        # Is the auth_class defined in the config file?      
        if self.cfg.has_option('honeypot','auth_class'):         #包含auth_class值：UserDB
            authclass = self.cfg.get('honeypot','auth_class')
            authmodule = "cowrie.core.auth"

            # Check if authclass exists in this module
            if hasattr(modules[authmodule],authclass):              #模块中有此
                authname = getattr(modules[authmodule],authclass)
            else:
                log.msg('auth_class: %s not found in %s' %
                    (authclass,authmodule))

        theauth = authname(self.cfg)