class Person({name:"bill", addr:"foo"}):
#there's no syntax for object literals in Python
#such a thing doesn't even make sense: so I'm improvising.
pass
charlie = Person()
charlie.name = "charlie"
charlie.addr = "baz"
class NewPerson(charlie):
#note charlie is an object, not a class
pass
bill = NewPerson()
In JS, charlie isn't a class, charlie is an object: you can change all its properties and everything, just like any other object. It's not a class, because there aren't any.Brush up on your Python skills before talking rubbish.
In any case you're not actually providing any links or facts, so unless I dig through long articles on metaclasses in python, I can't verify anything you say. Please prove your point, or at least provide I link so I can verify.
It should be interesting to see if I can actually abuse Python's meta-programming enough to make it work :-)
Right; this is actually why I like Python's way a bit better: it makes a more formal distinction between the two. In Python, Charlie is also an object, and you can change all its properties and everything, just like most¹ other objects.
Most of what you try to use to distinguish JS from Python applies just as well to Python. No, it isn't exactly the same, and I think the semantically equivalent code in Python will often contain more information than the JS. E.g., in my conversion of your JS, the class is an instance of `type`, whereas — as you correctly note — it's "just" an object in JS. It's not really though; in most JS that devs will write, the object is a type, but that distinction isn't explicit in the code. It's implicit in the dev's intentions, expressed only in the general sense that the code is being used.
e.g., if I saw, in JS,
var Person = function(){};
Person.prototype = {name:"bill", addr:"foo"};
var charlie = new Person();
while it is true, technically, that `Person` is a function and `Person.prototype` is an object, the semantic meaning being expressed in this manner by the author of this setup is that `Person` is a type, and that charlie is an instance of that type. It's just explicit in Python. (To some degree, JS is aware of this fact too; `charlie instanceof Person` is `true`, after all.)In a single-inheritance class in Python, during attribute lookup, Python will attempt to look the attribute up on the object's __dict__; if it doesn't exist, then it looks up the parent type (by looking at __class__) and then recurses, trying to look the attribute up there, and proceeding up the "chain".²
In JS, during attribute lookup, JS will attempt to look the attribute up on the object's internal list of attribute (I don't believe this is exposed like __dict__ in Python); if it doesn't exist, then it looks up the parent type (by looking at __proto__) and then recurses, trying to look the attribute up there, and proceeding up the "chain".
What material difference exists here?
¹objects in Python can forbid attributes from being set, or limit the available attributes. I'm not sure to what extend JS lets you do that. e.g., `object` in Python is very restrictive about allowing additional objects.
²I'm explicitly ignoring multiple inheritance here, so I'm vastly simplifying. Python will actually use the MRO for this procedure, but in the case of simple inheritance, that's equivalent to following __class__. I'm also ignoring __slots__ for simplicity.
Yes, but it's (roughly speaking) an instance of a "Class" class. In the "Person" example, the prototype of a "Person" object is another "Person" object (until the chain reaches an "Object", at least).
A type in Python is also just another object. When a method is called, or a variable is looked up on an object, Python scans the MRO (effectively the same thing as the prototype chain, except it supports multiple inheritance too) all the way up to `object`.
Python's type system is very similar, if not nearly a superset (though probably not exactly), of JavaScript's. I struggle to see the real material differences in them.
Consider your example, translated: