如何知道一个对象是否在 Python 中有一个属性 [英] How to know if an object has an attribute in Python

问题描述

在 Python 中有没有办法确定一个对象是否具有某些属性?例如:

Is there a way in Python to determine if an object has some attribute? For example:

>>> a = SomeClass()
>>> a.someProperty = value
>>> a.property
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: SomeClass instance has no attribute 'property'

如何判断a在使用前是否有属性property?

How can you tell if a has the attribute property before using it?

推荐答案

试试<代码>hasattr():

if hasattr(a, 'property'):
    a.property

请参阅下面的 zweiterlinde 的回答，他提供了关于请求宽恕的好建议！一个非常pythonic的方法！

See zweiterlinde's answer below, who offers good advice about asking forgiveness! A very pythonic approach!

python 中的一般做法是，如果该属性可能大部分时间都存在，则只需调用它并让异常传播，或者使用 try/except 块捕获它.这可能比 hasattr 更快.如果该属性可能大部分时间都不存在，或者您不确定，使用 hasattr 可能会比反复陷入异常块更快.

The general practice in python is that, if the property is likely to be there most of the time, simply call it and either let the exception propagate, or trap it with a try/except block. This will likely be faster than hasattr. If the property is likely to not be there most of the time, or you're not sure, using hasattr will probably be faster than repeatedly falling into an exception block.

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