python - 在Python中检查类型的规范方法是什么？(What's the canonical way to check for type in Python?)

Question

What is the best way to check whether a given object is of a given type?

(检查给定对象是否为给定类型的最佳方法是什么？)

How about checking whether the object inherits from a given type?

(如何检查对象是否从给定类型继承？)

Let's say I have an object o .

(假设我有一个对象o 。)

How do I check whether it's a str ?

(如何检查是否为str ？)

  ask by Herge translate from so

Answer 1

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

(要检查是否o是的实例str或的任何子类str ，使用isinstance （这将是“规范”的方式）：)

if isinstance(o, str):

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

(要检查o的类型是否完全是str （不包括子类）：)

if type(o) is str:

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

(以下内容也可以使用，并且在某些情况下可能有用：)

if issubclass(type(o), str):

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

(有关相关信息，请参见Python库参考中的内置函数 。)

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

(还有一点需要注意：在这种情况下，如果您使用的是python 2，则实际上可能要使用：)

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 ).

(因为这也会捕获Unicode字符串（ unicode不是str的子类； str和unicode都是basestring子类）。)

Note that basestring no longer exists in python 3, where there's a strict separation of strings ( str ) and binary data ( bytes ).

(请注意，在python 3中不再存在basestring ，在Python 3中，字符串（ str ）和二进制数据（ bytes ） 严格分开 。)

Alternatively, isinstance accepts a tuple of classes.

(另外， isinstance接受一个类的元组。)

This will return True if x is an instance of any subclass of any of (str, unicode):

(如果x是（str，unicode）的任何子类的实例，则将返回True：)

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