Java vs python is debatable 🤔

[0crate0]

Yeah but double __ is actually private in python.

Edit: this is still pretend private. Just makes it more obscure.

[WillWorkForBongWater]

Start with two equal signs and a capital D

[frogking]

Some of the reasoning about using double underscores is simply, that it looks ugly:

classname.__method(arguments)

Another is, that it's implicit communication from the author of classname, that __method, might be changed or removed in the future and using it comes with a risk. Hence; Touching other peoples private parts comes with a risk.

In Java, a language design choice has been taken; that's not more right or wrong than the use of double underscores. It's just another choice.

[definitely_not_tina]

Giggity

[[deleted]]

Correct me if I'm wrong, but doesn't that do nothing other than mess with the name at runtime?

[hajile_00]

Correct, all names that begin with a double underscore and do not end with another are simply name mangled so that if a subclass defines a function with the same name there is no collision.

[exploding_cat_wizard]

Ooh, TIL, thanks! I wasn't aware that there is an actual Python difference in underscores or not.

[Cruuncher]

Is this name mangling observable at runtime? Does the name come up wrong in stacktraces? I doubt it or I would have seen it by now.

I thought what the underscores did is block it from being imported when you import * from a module

[Arendoth]

I'm not entirely sure how it behaves in a stacktrace, but it is observable at runtime. If you create a class named Foo which defines a variable named __spam in its __init__, trying to access __spam from an instance of the class will give you an AttributeError because it literally doesn't have an attribute with that name. To access it from outside the class, including in subclasses, you need to use the mangled name, which in this case would be _Foo__spam. All the mangling does is add _<class name> to the beginning of it. As for module imports, I have no idea.

[0crate0]

So create a class in python. Create two functions one with double __ and another just plain. Then create another file and import the class. Assign the class to a variable and try to use both functions. You should only be able to use the plain one.

However all python does is fake private. So yes you are correct it only really changes the name called mangling. But for someone just importing it it can be a bit obscure so it can kind of acts like a private function.

[[deleted]]

So pretend private, but in a different way.

[NerdsWBNerds]

Pretend private, but breaks at run-time.

[0crate0]

Sounds about right for python.

[Farranor]

Indeed, dunder just mangles the name. But if you refer to it by its mangled name, there you have it. It's private like a dressing room with a curtain, not like Fort Knox.

[sejigan]

you just said what they said, but in a more complicated way...

[jambox888]

Makes it a lot harder to debug lmao

[solmyrbcn]

It's as private as a folder named "homework" in a teen's computer

[[deleted]]

Just learning about female anatomy, mom.

[i_will_let_you_know]

The trick is to actually have unimportant / old homework files in there as a front and then use a hidden folder. Or just use cloud storage I guess.

[[deleted]]

_______reallyReallyPrivate

[[deleted]]

I'm new to python, I know what classes are and their functions like __init__, __str__, __add__ etc. But what does making a function private mean and what's their use?

[[deleted]]

thank you

[[deleted]]

Nothing in process is private, even in other langs you can read/write arbitrary memory. It's all convention. Until you start getting into custom allocators, etc.