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Mind your own business, Spock. I'm sick of your halfbreed interference.

devel / comp.lang.python / Re: Why doc call `__init__` as a method rather than function?

Re: Why doc call `__init__` as a method rather than function?

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From: cs...@cskk.id.au (Cameron Simpson)
Newsgroups: comp.lang.python
Subject: Re: Why doc call `__init__` as a method rather than function?
Date: Mon, 18 Sep 2023 15:16:42 +1000
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by: Cameron Simpson - Mon, 18 Sep 2023 05:16 UTC

On 15Sep2023 10:49, scruel tao <scruelt@hotmail.com> wrote:
>```python
>>>> class A:
>... def __init__(self):
>... pass
>...
>```
>
>On many books and even the official documents, it seems that many authors prefer to call `__init__` as a "method" rather than a "function".
>The book PYTHON CRASH COURSE mentioned that "A function that’s part of a class is a method.", however, ` A.__init__` tells that `__init__` is a function...

As mentioned, methods in Python _are_ functions for use with a class.

>>>> A.__init__
><function A.__init__ at 0x0000026CFC5CCEE0>
>>>> a = A()
>>>> a.__init__
>
><bound method A.__init__ of <__main__.A object at 0x0000026CFC1BB400>>
>I wonder how can I call `__init__` as? Consider the output above.
>Maybe both are OK?

As you can see, they're both legal expressions.

The thing about `__init__` is that it's usually called automatically
which you make a new object. Try putting a `print()` call in your
`__init__` method, then make a new instance of `A`.

The purpose of `__init__` is to initialise the object's attribute/state
after the basic, empty-ish, object is made.

Like other dunder methods (methods named with double underscores front
and back) it is called automatically for you. In a subclass the
`__init__` method calls the subperclass `__init__` and then does
whatever additional things might be wanted by the subclass.

Let's look at what you used above:

>>> A.__init__
<function A.__init__ at 0x0000026CFC5CCEE0>

Here's we've just got a reference to the function you supposlied with
the class definition for class `A`.

This:

>>> a = A()
>>> a.__init__
<bound method A.__init__ of <__main__.A object at 0x0000026CFC1BB400>

Here's you've accessed the name `__init__` via an existing instance of
`A`, your variable `a`. At this point you haven't called it. So you've
got a callable thing which is a binding of the function to the object
`a` i.e. when you call it, the "bound method" knows that t is associated
with `a` and puts that in as the first argument (usually named `self`).

Cheers,
Cameron Simpson <cs@cskk.id.au>

Subject	Author
Re: Why doc call `__init__` as a method rather than function?	Cameron Simpson