Calling a class function without triggering the __init__

Question

Is there any way to call functions inside a class without triggering the __init__ part of that class? Let's say I have the next class, usually I'd call the function this way:

class Potato():
    def __init__(self):
        print("Initializing")
    def myfunction(self):
        print("I do something")

Potato().myfunction()

But as expected that prints the Initializing part. Now, If I wanted to call myfunction without triggering that. How would you do it? Pros and cons of doing it? It's even possible?

Answer 1

Not sure if this is what you're looking for, but:

A classmethod or a staticmethod could be used without creating an instance of the class - which means that init would not be called that way:

class MyClass:
   def __init__(self):
      print("Initialize instance - not used")

   @staticmethod
   def my_static(toprint):
       print(toprint)

MyClass.my_static("Print this")

Answer 2

Yes, it is possible.

Using a helper function

You could write a helper function that replace __init__ method of your class with a dummy method and then instantiates the class and after this we re-assign the old __init__ back to class.

def skip_init(cls):
    actual_init = cls.__init__
    cls.__init__ = lambda *args, **kwargs: None
    instance = cls()
    cls.__init__ = actual_init
    return instance

Demo:

>>> a = skip_init(Potato)
>>> a.myfunction()
I do something

---

Overriding __new__

You could override __new__ method of your class and there based on argument you can replace __init__ with a dummy method.

def new_init(cls, init):
    def reset_init(*args, **kwargs):
        cls.__init__ = init
    return reset_init


class Potato():
    def __new__(cls, *args, **kwargs):
        instance = object.__new__(cls)
        lazy = kwargs.pop('_no_init', False)
        if not lazy:
            return instance
        cls.__init__ = new_init(cls, cls.__init__)
        return instance

    def __init__(self):
        print("Initializing")

    def myfunction(self):
        print("I do something")

Demo:

>>> a  = Potato(_no_init=True)
>>> a.myfunction()
I do something
>>> b  = Potato()
Initializing
>>> b.myfunction()
I do something