Python 3.9 如果一个字符串匹配一个class的名字，实例化class（动态实例化具体的class）

Question

I would like to instantiate a single class if a string var matches the name of the class. In similar questions, there seems to be a dependency that the name of the class is known at the start. In my case, I only know that the input string will match the name of a class. I want to use the string to identify which class (out of many choices) I need to instantiate. IE load the class with the same name as the string;

If string-var == a class (in a module file) in a directory, instantiate that class.

I thought the new getattr would help, but that seems to be for methods/functions as opposed to a class itself. I also considered issubclass, but the parameter needs to be a class, not a string. Any suggestions are greatly appreciated!

Answer 1

You should explicitly define an interface that maps a publicly known string to a reference to the class:

class Foo:
    ...

class Bar:
    ...

classes = {"foo": Foo, "bar": Bar}

Then you can lookup the appropriate class in the dict using your string (which, as you'll note, is not required to be the name of the class):

cls_name = "foo"

obj = classes[cls_name]()