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From: "Peter J. Holzer" <hjp-python@hjp.at>
Newsgroups: comp.lang.python
Subject: Re: Difference method vs attribut = function
Date: Sat, 29 Jun 2024 21:53:05 +0200
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On 2024-06-28 18:08:54 +0200, Ulrich Goebel via Python-list wrote:
> a class can have methods, and it can have attributes, which can hold a
> function. Both is well known, of course.
>=20
> My question: Is there any difference?
>=20
> The code snipped shows that both do what they should do. But __dict__
> includes just the method,
The other way around: It includes only the attributes, not the methods.
> while dir detects the method and the
> attribute holding a function. My be that is the only difference?
>=20
>=20
> class MyClass:
> def __init__(self):
> functionAttribute =3D None
> =20
> def method(self):
> print("I'm a method")
>=20
> def function():
> print("I'm a function passed to an attribute")
Here is the other main difference: The object is not passed implicitely
to the function. You have no way to access mc here.
You can create a method on the fly with types.MethodType:
import types
mc.functionAttribute =3D types.MethodType(function, mc)
> By the way: in my usecase I want to pass different functions to
> different instances of MyClass. It is in the context of a database app
> where I build Getters for database data and pass one Getter per
> instance.
Or in this case, since each function is specific to one instance, you
could just use a closure to capture the object. But that might be
confusing to any future maintainers (e.g. yourself in 6 months), if the
method doesn't actually behave like a method.
hp
--=20
_ | Peter J. Holzer | Story must make more sense than reality.
|_|_) | |
| | | hjp@hjp.at | -- Charles Stross, "Creative writing
__/ | http://www.hjp.at/ | challenge!"
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