python - 如何将默认参数与multipledispatch一起使用？

Question

我正在使用默认参数重载函数multipledispatch（基于this answer）

from multipledispatch import dispatch

class TestExampleTest(AbstractTest):
    @dispatch(ClassOne, bool, bool)
    def function(self, my_class, a=True, b=True):
        do_something()

    @dispatch(ClassTwo, bool)
    def function(self, my_class, a=True):
        do_something_else()

当我在function()没有将值传递给boolitem/s的情况下调用 a

self.function(ClassOne())

我明白了

NotImplementedError：找不到函数的签名

完整的堆栈跟踪：

ExampleTest.py:27 (TestExampleTest.test_example_test)
self = <ExampleTest.TestExampleTest object at 0x04326BB0>

    def test_example_test(self):
>       self.function(ClassOne())

ExampleTest.py:29: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <dispatched function>
args = (<ExampleTest.ClassOne object at 0x043262B0>,), kwargs = {}
types = (<class 'ExampleTest.ClassOne'>,), func = None

    def __call__(self, *args, **kwargs):
        types = tuple([type(arg) for arg in args])
        func = self.dispatch(*types)
        if not func:
            raise NotImplementedError('Could not find signature for %s: <%s>' %
>                                     (self.name, str_signature(types)))
E           NotImplementedError: Could not find signature for function: <ClassOne>

..\..\..\..\Automation\lib\site-packages\multipledispatch\dispatcher.py:434: NotImplementedError

注意：我知道我可以@dispatch一起放下并做类似的事情

def function(self, my_class_one=None, my_class_two=None, a=True, b=True):
    if my_class_one:
        do_something()
    elif my_class_two:
        do_something_else()

但我想知道我是否可以保留当前的结构。

我该如何解决？

标签： pythonpython-3.xmultiple-dispatch

Answer 1

默认参数应该在@dispatch 中声明为关键字参数，然后如果要在调用这些函数时修改具有默认值的参数值，请记住传递关键字而不是依赖位置。

from multipledispatch import dispatch

class TestExampleTest(AbstractTest):
    @dispatch(ClassOne, a=bool, b=bool)
    def function(self, my_class, a=True, b=True):  # 1st function
        do_something()

    @dispatch(ClassTwo, a=bool)
    def function(self, my_class, a=True):          # 2nd function
        do_something_else()


test_ins = TestExampleTest()

# call 1st function
test_ins.function(class_one_ins) 
test_ins.function(class_one_ins, a=False)
test_ins.function(class_one_ins, a=False, b=False)

# call 2nd function
test_ins.function(class_two_ins)
test_ins.function(class_two_ins, a=False)