Python 3.5 type hinting gives "AttributeError: module 'iterator_function' has no attribute 'IteratorFunction'"

Question

当我尝试向我的自定义 class 键入提示时，python 将在 'module.class' 上抛出 AttributeError。 Intellisence告诉我，import是对的，可以找到class

function_dispatcher.py，这个文件在 : iterator_function.IteratorFunction 处出错。当我删除特定类型提示时，程序将运行正常。

from abc import ABC, abstractclassmethod
import iterator_function

class FunctionDispatcher(ABC):
    @abstractclassmethod
    def dispatch(self, function : iterator_function.IteratorFunction):
        pass

iterator_function.py，这是导入的class。注意：提示 : function_dispatcher.FunctionDispatcher 的类型在这里有效。

import function
import function_dispatcher

class IteratorFunction(function.Function):
    def accept(self, dispatcher : function_dispatcher.FunctionDispatcher):
        dispatcher.dispatch(self)

这是回溯输出：

1>  Traceback (most recent call last):
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\main.py", line 1, in <module>
1>      import generator
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\generator.py", line 3, in <module>
1>      from iterator_function import IteratorFunction
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\iterator_function.py", line 1, in <module>
1>      import function
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\function.py", line 2, in <module>
1>      import function_dispatcher
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\function_dispatcher.py", line 4, in <module>
1>      class FunctionDispatcher(ABC):
1>    File "C:\Users\admin\Documents\visual studio 2015\Projects\Preprocessor\Program\preprocessor\function_dispatcher.py", line 6, in FunctionDispatcher
1>      def dispatch(self, function : iterator_function.IteratorFunction):
1>  AttributeError: module 'iterator_function' has no attribute 'IteratorFunction'

对于任何想知道我正在尝试做什么的人：实施 visitor pattern.

Answer 1

hiro protagonist 是对的。我能够解决循环导入并维护类型检查。它不是那么干净，但可以完成工作。

function.py

from abc import ABC, abstractmethod

class Function(ABC):
    def __init__(self, arguments, min_arguments):
        self.arguments = arguments
        self.min_arguments = min_arguments if len(arguments) < min_arguments else len(arguments)

    @abstractmethod
    def accept(self, dispatcher):
        pass

    def test_dispatcher(self, dispatcher):
        import function_dispatcher
        if not isinstance(dispatcher, function_dispatcher.FunctionDispatcher):
            raise Exception("Not of type FunctionDispatcher")

迭代器_function.py

import function

class IteratorFunction(function.Function):
    def accept(self, dispatcher):
        self.test_dispatcher(dispatcher)
        dispatcher.dispatch(self)

Python 3.5 type hinting gives "AttributeError: module 'iterator_function' has no attribute 'IteratorFunction'"

Python 3.5 type hinting gives "AttributeError: module 'iterator_function' has no attribute 'IteratorFunction'"

visitor-pattern

type-hinting

python-import

attributeerror

python-3.x