如何在Python类中顺序调用未定义的方法

Question

With getattr , I can do it like this : myclass.method1()

But I'm looking for something like myclass.method1().method2() or myclass.method1.method2() .

It means that method1 , method2 are not defined in the class.

Is there any way to call undefined methods sequentially in a Python class?

Answer 1

I am not really sure, but it seems that what you are calling the undefined method is actually a normal method which you just want to call by name (because you obviously can not call something that is really not defined).

In this case, you can nest getattr as many times as you need to go deeper, here is an example:

class Test:
    def method_test(self):
        print('test')


class Another:
    def __init__(self):
        self._test = Test()
    def method_another(self):
        print('Another')
        return self._test

another = Another()
getattr(
    getattr(another, 'method_another')(),
    'method_test'
)()

The last statement actually does another.method_another().method_test() .

Answer 2

This is what exactly that I've looked for:

class MyClass:
    def __getattr__(self, name):
        setattr(self, name, self)
        def wrapper(*args, **kwargs):
            # calling required methods with args & kwargs
            return self
        return wrapper

Then I can call undefined methods sequentially like so:

myclass = MyClass()
myclass.method1().method2().method3()

Answer 3

@Mortezaipo: You should set the attribute to the wrapper method, otherwise you can call the undefined methods only once:

class MyClass:
    def __getattr__(self, name):
        def wrapper(*args, **kwargs):
            # calling required methods with args & kwargs
            return self
        setattr(self, name, wrapper)
        return wrapper