Overriding Python str class setter.. How?

Coding another tool in python as usual i was getting tired of printing several debug messages. The script performs some calls to multiple main methods that in turn call other secondary  methods. I wanted to track the final status of each call so i thought that it would be a good idea to print a message each time a "msg" object changes its value. Thus recurring to the 'set value triggers function call' paradigm.

One solution i found was to create a new class that inherits from "object" and use @property and @<member>.setter with an intermediate string object to store the text.

But i wasn't satisfied enough and coming from C++ i was wondering if it was possible to inherit directly from "str" class and just override its setter.

Since i found no info on the web, i resorted to write to a tech forum. 

Here is my post:


I'm coding a script that performs different complex tasks and i want to output status messages regarding the execution of the script.
Rather than doing a "print" statement after each main function call i 've thought it would be nicer to have a string object that automatically prints something each time the variable's value changes.
So this lead me to write a custom class with a variable and a setter to it like the following:

Code:

class Msg(object):
    def __init__(self):
        self._s = None
    
    @property
    def status(self):
        return self._s
    @status.setter
    def status(self, value):
        self._s = value
        call_custom_function()

Now the question: I've come to the above solution but i'm wondering if it's possible to inherit directly from str class and just override the setter... thus not needing an intermediate variable like _s and be able to do something like

Code:

msg = Msg()
msg = "hello"

instead of the current:

Code:

msg = Msg()
msg.status = "hello"

I've searched the web and i haven't found how the str class works besides the fact that it's a "sequencer" type just like a list...

The same day i received several answers that despite interesting were missing the point of my question, until i got finally the explanation.

Here is the final reply that enlighted me:

Code:

msg = Msg()
msg = "hello"

to anyone who write python code, these lines mean this:

1. Create an instance of the class Msg and assign it to msg
2. msg is now the string "hello"

Your instance of the Msg class has been overwritten. Thats why it makes no sense. Why create an isntance of a class just to over-write it with a string.

Ahhhh this is what i was getting wrong!!! In a language like C++ one can overload the "=" operator and hence the second line would call the overloaded method from the "=" operator from the msg instance of Msg() Class. The type of "msg" doesnt change!!!!

But in Python we dont have such behaviour, so when we assign "hello" we are just changing the type of the variable to be a string!!