Python从具有函数的类返回值

Question

I would like to have a class like this:

class Test:
    def __new__(cls):
        return 'test'

    def hi(self):
        print('hi')

As you can see, I would like to create a class that returns a value on instantiation, but still uses the functions of the class, so like this:

cl = Test()
print(cl)
cl.hi()

If anyone can help me, that would be great!

Answer 1

You want this:

class Test:

    def hi(self):
        print('hi')

    def __str__(self):
        return 'test'

cl = Test()
print(cl)
cl.hi()

The method __str__(self) is setting the behavior for the class when used as a string.

Answer 2

I think you're looking for something like this.

class Test:
    def __init__(self):
        pass

    def __str__(self):
        return 'test'

    def hi(self):
        print('hi')

Special Method names could be a good read for you. https://docs.python.org/3/reference/datamodel.html

Answer 3

or maybe this... class TestMe:

def __init__(self):
    print('init')

def hi(self):
    print('hi')

Answer 4

This does not change the MRO or the class type. It still needs some work.

class MethodAdder:
    def __init__(self, obj):
        self._obj = obj

    def __str__(self):
        return str(self._obj)

    def __eq__(self, other):
        return self._obj == other

    def __ne__(self, other):
        return self._obj != other

    # ... and so on

    def __setattr__(self, key, value):
        try:
            if hasattr(object.__getattribute__(self, "_obj"), key):
                setattr(object.__getattribute__(self, "_obj"), key, value)
        except AttributeError:
            pass
        object.__setattr__(self, key, value)

    def __getattribute__(self, item):
        try:
            if hasattr(object.__getattribute__(self, "_obj"), item):
                return getattr(object.__getattribute__(self, "_obj"), item)
        except AttributeError:
            pass
        return object.__getattribute__(self, item)

    def hello(self):
        print("hello2")


v = MethodAdder("test")
print(v)
v.hello()
print(v.split("e"))