在 Python 中检查类型的规范方法是什么? [英] What's the canonical way to check for type in Python?

问题描述

检查给定对象是否属于给定类型的最佳方法是什么?如何检查对象是否继承自给定类型?

假设我有一个对象 o.如何检查它是否是 str?

解决方案

检查 o 是否是 str 的实例或 str，使用isinstance(这将是规范"方式):

if isinstance(o, str):

检查o的类型是否正好是str(排除子类):

如果 type(o) 是 str:

以下也有效，并且在某些情况下很有用:

if issubclass(type(o), str):

有关相关信息，请参阅 Python 库参考中的内置函数.>

再注意:在这种情况下，如果您使用的是 Python 2，您可能实际上想要使用:

if isinstance(o, basestring):

因为这也会捕获 Unicode 字符串(unicode 不是 str 的子类；str 和 unicode 都是 basestring).请注意，basestring 在 Python 3 中不再存在，其中有 严格分离 字符串 (str)和二进制数据(字节).

或者，isinstance 接受一个类元组.如果 o 是任何 (str, unicode) 的任何子类的实例，这将返回 True:

if isinstance(o, (str, unicode)):

What is the best way to check whether a given object is of a given type? How about checking whether the object inherits from a given type?

Let's say I have an object o. How do I check whether it's a str?

解决方案

To check if o is an instance of str or any subclass of str, use isinstance (this would be the "canonical" way):

if isinstance(o, str):

To check if the type of o is exactly str (exclude subclasses):

if type(o) is str:

The following also works, and can be useful in some cases:

if issubclass(type(o), str):

See Built-in Functions in the Python Library Reference for relevant information.

One more note: in this case, if you're using Python 2, you may actually want to use:

if isinstance(o, basestring):

because this will also catch Unicode strings (unicode is not a subclass of str; both str and unicode are subclasses of basestring). Note that basestring no longer exists in Python 3, where there's a strict separation of strings (str) and binary data (bytes).

Alternatively, isinstance accepts a tuple of classes. This will return True if o is an instance of any subclass of any of (str, unicode):

if isinstance(o, (str, unicode)):

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