如何更改传递给Python中类中函数的属性

Question

这可能是我的强迫症，但我写了一些代码，我只是想知道是否有一种优雅的方法来更改传递给 python 类中函数的属性？我下面有一些示例代码（我正在尝试更改 on_message 的值）：

# my_class is defined in an external library

class my_class: 
    def __init__(self, stream_url="wss://stream.default:6969/ws", on_message=None):
        super().__init__(stream_url, on_message=on_message)
        
    def my_function(self, key: str, **kwargs):
        # do stuff to key and kwargs

# my python code

ws_client = my_class(stream_url="wss://stream.actual:6969/ws") # this is at the top of the file where all other declarations are made, as there is no on_message value passed to the class, it's value is None as per __init__ function

def do_stuff_with_message(): # this happens about 3/4 through
    # do stuff to with the message

ws_client = my_class(on_message=do_stuff_with_message) # this works but seems clumsy and like a redeclaration. Is there a more pythonic way of doing this?

ws_client.my_function(key="Dante")

如上所述，代码有效，我只是在寻找更简洁的解决方案，甚至可能是 do_stuff_with_message 的前向声明。任何建议，将不胜感激。谢谢。

Answer 1

感谢大家的帮助和评论。我设法用（一种前向声明）“修复”它：

# my_class is defined in an external library

class my_class: 
def __init__(self, stream_url="wss://stream.default:6969/ws", on_message=None):
    super().__init__(stream_url, on_message=on_message)
    
def my_function(self, key: str, **kwargs):
    # do stuff to key and kwargs   

# my python code

def Do_Stuff_With_Message():
    do_stuff_with_message()

ws_client = my_class(stream_url="wss://stream.actual:6969/ws", on_message=Do_Stuff_With_Message) # this is at the top of the file where all other declarations are made, as there is no on_message value passed to the class, it's value is None as per __init__ function

def do_stuff_with_message(): # this happens about 3/4 through
    # do stuff to with the message

ws_client.my_function(key="Dante")

再次感谢。

Answer 2

首先，看起来您正在用

ws_client

中的类的新实例覆盖

ws_client = my_class(on_message=do_stuff_with_message)

。如果您想添加或更改属性，可以使用

ws_client.on_message = do_stuff_with_message

。

另外，

super().__init__

用于在继承时初始化父类。您不会在这里执行此操作，因此不需要。

class my_class: 
    def __init__(self, stream_url="wss://stream.default:6969/ws"):
        # super().__init__(stream_url, on_message=on_message) does not do anything as my_class is not inheriting from another class
        self.stream_url = stream_url
        
    def my_function(self, key: str, **kwargs):
        # do stuff to key and kwargs

ws_client = my_class(stream_url="wss://stream.actual:6969/ws")

def do_stuff_with_message():
    # do stuff to with the message

ws_client.on_message = do_stuff_with_message # on_message does not need to be declared in __init__.
                                             # In your original code you created a new instance or your class. This code modifies the existing object

ws_client.my_function(key="Dante")