class Classname(object), what sort of word is 'object' in Python?

Question

When I create a module with its sole content:

class Classname(randomobject):
    pass

And I try to run the .py file of the module the interpreter says that randomobject is not defined.

But when I do:

class Classname(object):
    pass

The module runs just fine. So if object is not a keyword, then what is it?

Here's another question which addresses the Python `object` identifier: [python class inherits object](http://stackoverflow.com/q/4015417/404469). — gary, Jan 03 '13 at 22:16
For the record, http://stackoverflow.com/q/4015417/404469 is not a duplicate. It's about the mechanism of inheritance; this question is about, and has multiple answers about, the syntactic structure of what's going on. — Marcin, Jun 18 '17 at 16:54

Marcin · Accepted Answer · 2012-04-06T14:04:55.120

32

object is a (global) variable. By default it is bound to a built-in class which is the root of the type hierarchy.

(This leads to the interesting property that you can take any built-in type, and use the __bases__ property to reach the type called object).

Everything built-in that isn't a keyword or operator is an identifier.

edited Apr 06 '12 at 14:04

answered Apr 06 '12 at 13:58

Marcin

Thank you. I assume you can't view the code what is being assigned to this global variable? – Bentley4 Apr 06 '12 at 16:15
@Bentley4 I don't know what you mean. – Marcin Apr 06 '12 at 16:25
I'm sorry. In /usr/lib/python2.7 you can find the standard python modules. By opening the python files yourself you can see variable assignments, bodies of the classes and functions etc. of the modules that you can't see by using the help function. Is there any way to access the __builtin__ module and look at the object variable in that module? – Bentley4 Apr 06 '12 at 17:15
1

@Bentley4 I've never tried. Consider grepping for it; if not, you'll have to find it in the C source. – Marcin Apr 06 '12 at 17:16

score 17 · Answer 2 · answered May 23 '19 at 13:26

The following three class declarations are identical in Python 3

class Classname(object):
    pass

class Classname():
    pass

class Classname:
    pass

Well, there will be minor differences, but not fundamentally important since the object class is the base for all.

If you plan to write Python agnostic code (Python2 and Python3 agnostic) you may use the first declaration.

Taymon · Answer 3 · 2012-04-06T14:04:28.550

8

object is an identifier that refers to a builtin type.

Unlike many other languages, there are no primitive types in Python. Everything is an object, including all data types.

I'm not sure why you expected inheriting from randomobject to work.

edited Apr 06 '12 at 14:04

answered Apr 06 '12 at 13:43

Taymon

Perhaps I wasn't entirely clear; I meant that `object` doesn't have special syntactic or semantic significance in Python the way, say, `int` does in Java. – Taymon Apr 06 '12 at 14:00
Strictly, the "type of word that object is" is a variable, for that reason. – Marcin Apr 06 '12 at 14:02
1

Updated answer to reflect this. – Taymon Apr 06 '12 at 14:04

Kien Truong · Answer 4 · 2012-04-06T13:52:25.787

7

object is the base class from which you inherit when creating a new-style class in Python 2.

edited Apr 06 '12 at 13:52

answered Apr 06 '12 at 13:45

Kien Truong

It's not necessary to do this in Python 3.x, however. New-style classes are the default. – Gareth Latty Apr 06 '12 at 13:50
1

In Python 3, all classes still inherit from object. In addition, "the type of word that object is" is an identifier. – Marcin Apr 06 '12 at 14:06

4 Answers4