“AttributeError: 'NoneType' 對象沒有屬性 'test'” 使用上下文管理器

Question

我有這門課：

class Tess:
    def __init__(self, **kwargs):
        self.kwargs = kwargs

    def __enter__(self):
        print('fire away!')
        for key, value in self.kwargs.items():
            print(f"{key} and {value}")

    def __exit__(self):
        print('the end.')

    def test(self, **kwargs):        # This takes in a different dict independent of __init__
        # Also tried self.kwargs = kwargs here but doesn't change anything
        for key, value in self.kwargs.items():
            print(f"The end of {key} and {value}")
        

然后我在上下文管理器中使用它。

with Tess(foo='bar') as t:
    t.test(foo_bar='baz')

我預計輸出是：

fire away!
foo and bar
The end of foo_bar and baz
the end.

相反，它給出：

Traceback (most recent call last):
  File "/...", line 145, in <module>
    t.test(foo_bar='baz')
AttributeError: 'dict' object has no attribute 'test'

我該如何糾正？ 謝謝。

Answer 1

檢查這個：

class Tess:
    def __init__(self, **kwargs):
        self.kwargs = kwargs

    def __enter__(self):
        print('fire away!')
        for key, value in self.kwargs.items():
            print(f"{key} and {value}")
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        print('the end')

    def test(self, **kwargs):  # This takes in a different dict independent of __init__
        # Also tried self.kwargs = kwargs here but doesn't change anything
        for key, value in self.kwargs.items():
            print(f"The end of {key} and {value}")


with Tess(foo='bar') as t:
    t.test(foo_bar='baz')

輸出 ：

fire away!
foo and bar
The end of foo and bar
the end

我做了兩個改變：

1- 為了在as t語句中訪問t ，您應該將return self放在__enter__ 。 t將是您從__enter__返回的任何__enter__

2- Python 將exc_type 、 exc_val 、 exc_tb （類型、值、回溯）傳遞給__exit__方法，因此您應該更改簽名以接受這些參數。