Earlier quoted context omitted.
> can you name some OOP features Java has that Python doesn't have? Encapsulation. In Python you can write code in an OO style and benefit from inheritance, but it’s really only good for people writing libraries and frameworks. For end user code, objects are best avoided because they can pick up state in unexpected ways, which leads to problems that are extremely difficult to debug.
Could you give some examples? What encapsulation features does Java have that Python doesn't? You can get private methods with double underscores. It's true that attributes in Python objects are all public by default and in Java you have to be more explicit to get public attributes, so maybe that counts, but otherwise what do you mean by "objects can pick up state in unexpected ways"?
class Foo():
def __init__(self):
self.bar = 1
You can see that foo_instance is imported from module A. So you go there, and see that the instance wasn't created there, it was imported from module B. But wait, it wasn't created there either, it was imported from module C, etc.
Somewhere along the way bar picked up the value of 2. But it's almost impossible to figure out where because there isn't any requirement use a uniquely-named accessor to modify the instance, so you can't just grep through the code to see where that method was called. (And maybe the name of the instance has changed a few times along the way, for whatever reason.)
And what's worse, the code that modified the instance might not even be visible in any of the modules, it's possible that someone took advantage of Python's ability to change the way the importing system works to mess with either the class or the instance. Or maybe there is some global middleware that's messing with objects or instances, or unrelated module Z is secretly monkey patching module B somewhere in the middle of this process. Who knows, and good luck figuring out.
Whereas if you just write the user-code logic in functions then it's not possible for developers to create situations like this. That obviously isn't possible for a library where the entire point is to make everything extensible and where you don't know how people will want to use something in advance, but hopefully the people writing libraries and frameworks have good enough judgment not to completely abuse the tools.
I'm not sure if I can really articulate how this is different than Java or Swift or whatever, but for whatever reason it just feels different.