On Tuesday, June 2, 2015 at 2:27:31 PM UTC+3, Steven D'Aprano wrote: > On Tue, 2 Jun 2015 08:36 pm, Eddilbert Macharia wrote: > > > you guys are just confusing me, you are going in loops, and still i have > > understood ,what makes everything in python an object. hey is where i'm at > > : *** type in python refers to data types e.g. int, str, boolean e.t.c. > > right ? > > Yes. Also classes you create with the "class" keyword: > > class K(object): > ... > > K is now a "type", just like int, str, list, object, etc. > > > > *** The interpreter creates two classes type and object when setting up a > > python environment. right ? > > Many more than just two: it also creates list, str, dict, etc. But *first* > it has to create type and object. So you are correct. > > > > *** The creator (metaclass) of all data types (i.e. int,str) in python is > > the class type. right ? > > Correct. > > [Aside: I'm only talking about Python 3 here. In Python 2 there is also a > second hierarchy of classes, called "classic classes" or "old-style > classes", which are *not* subclasses of type. But let's just ignore them, > because they are gone in the most recent versions of Python.] > > > >>>> isinstance(int,type) > > True > > > > *** The instance of class type is a data type an instance of class type. > > right ? > >>>> type(type) > > <class 'type'> > > type has many instances, not just one. > > Instances of int are individual ints, like 0, 1, 2, 3, ... > > Instances of type are individual types, like int, dict, str, list, ... > > But one of those many instances of type is, yes, type itself! So *one* of > the instances of type is type, which is also an instance of itself: > > >>>> isinstance(type,type) > > True > > Correct. This makes type special. Most types are *not* instances of > themselves: > > py> isinstance(int, int) > False > > > > *** Class type gets some of its behavior from class object through > > inheritance.right ? > > > >>>> issubclass(type,object) > > True > > Correct. > > > > *** instance of class object is type, in the sense it created using class > > type which inherits from class object.right ? > > > >>>> isinstance(object,type) > > True > >>>> isinstance(object,object) > > True > > > > ****so is it right to say, everything in python is an object because they > > are instance of the class type which inherits from class object ? > > No! That's not what we mean when we say "everything is an object". > > Eddilbert, have you programmed in any other languages? It would help you > understand if you have.
Sadly yes i have worked with java, and that is what is causing me so much grief.In java objects are instance of a class.pretty simple. > > "Object" has a general meaning in computer science and programming, it is a > compound data structure that is explicitly linked to a type which provides > functionality that operates on that data structure. > > In the programming language C, *no* values are objects. C has types (int16, > uint32, bool, and many more) but no objects. > > In the programming language Java, *some* values are objects, and some values > are not objects. > > In the programming language Python, *all* values are objects, in the general > sense. That is what we mean by "Everything is an object". > > Let's go back in time about 15 years or so. We're now using Python 1.5. In > Python 1.5, there is no built-in object, and type is just a function, not a > class: > > >>> import sys > >>> print sys.version > 1.5.2 (#1, Aug 27 2012, 09:09:18) [GCC 4.1.2 20080704 (Red Hat 4.1.2-52)] > >>> object > Traceback (innermost last): > File "<stdin>", line 1, in ? > NameError: object > >>> type > <built-in function type> > > > In Python 1.5, classes you create do not inherit from object, because object > does not exist! BUT even in Python 1.5, it is true that everything is an > object. > > Remember, "object" can refer to two things: > > - *specifically* the class called "object"; > > - the *general concept* of objects, from object oriented programming. > > > In Python 1.5: > > - everything is an object [the general concept] > > - nothing is an instance of the class called "object" > > > In Python 2: > > - everything is an object [the general concept] > > - some things, but not all things, are instances of the class > called "object" > > > In Python 3: > > - everything is an object [the general concept] > > - everything is an instance of the class called "object" > > > > I think then in python object and instance of a class are entirely different things. in OOP and python - object is a representation of a real thing, or a concept .e.g a person,number and the concept of classes- which is the concept of create/representing other objects using a programming language to the machine. class - This is what is used to create/represent objects in the machine using a programming language class instance - This is the output of the classes this is a representation of an object. > -- > Steven -- https://mail.python.org/mailman/listinfo/python-list
