在 python 类型提示中,如何让参数接受基类的任何子类? [英] In python type-hinting, how can I make an argument accept any subclass of a base class?
问题描述
我有一个看起来有点像这样的函数.我希望该函数接受 io.IOBase 的任何子类 - 换句话说,任何类似文件的对象.
I have a function that looks a bit like this. I want the function to accept any subclass of io.IOBase - in other words, any file-like object.
def import_csv_file(f:io.IOBase)->pandas.DataFrame:
return pandas.read_csv(f)
当我在 IntelliJ 中查看对象时,类型提示的 JetBrains 实现会拒绝任何输入,除非我提供了一个 io.IOBase 的实例——但是如果我想传入一个 io.IOBase 的子类的实例怎么办?数据库?有没有办法改变类型提示以说这是允许的?
When I view the object in IntelliJ, the JetBrains implementation of type-hinting rejects any input unless I provide exactly an instance of io.IOBase - but what if I want to pass in an instance of a sub-class of io.IOBase? Is there a way to change the type-hint to say that this is allowed?
推荐答案
如果您使用基类(io.IOBase
在您的情况下)注释函数参数,那么您还可以传递任何基类的子类型——继承也适用于注解类型.
If you annotate a function argument with the base class (io.IOBase
in your case) then you can also pass instances of any subtype of the base class – inheritance applies to annotation types as well.
也就是说,您可以使用 typing.IO
作为表示任何 I/O 流的泛型类型(以及分别用于二进制和文本 I/O 流的 typing.TextIO
和 typing.BinaryIO
).
That said, you could use typing.IO
as a generic type representing any I/O stream (and typing.TextIO
and typing.BinaryIO
for binary and text I/O streams respectively).
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