CODEWITHSUNDEEP
python
mythicalprogrammer
mythicalprogrammer

Reputation: 4737

Class with Object as a parameter

Why do some Python classes have an object parameter that's never explicitly used?

Example:

class Table(object)

Upvotes: 156

Views: 110109

Answers (6)

Anilkumar Mallakkanavar
Anilkumar Mallakkanavar

Reputation: 21

object is the most base type of class object defined in python. Attributes of object can be seen as below

**>>> dir(object)

['class', 'delattr', 'doc', 'format', 'getattribute', 'hash', 'init', 'new', 'reduce', 'reduce_ex', 'repr', 'setattr', 'sizeof', 'str', 'subclasshook']**

So Table(object) is just inheritance.!

Upvotes: 2

user6398989
user6398989

Reputation:

1)Class name (object): 2) class name: They both are same but first one quite better in terms of writing,it look better while inheriting other classes to another,i t looks homogeneous.

How same ? So,every thing in Python is come under object means every thing in Python has property of object,if write or don't it will understand it. In first we explicitly tell it in second we didn't.

Upvotes: 0

icktoofay
icktoofay

Reputation: 129001

The Table class is extending a class called object. It's not an argument. The reason you may want to extend object explicitly is it turns the class into a new-style class. If you don't explicitly specify it extends object, until Python 3, it will default to being an old-style class. (Since Python 3, all classes are new-style, whether you explicitly extend object or not.)

For more information on new-style and old-style classes, please see this question.

Upvotes: 38

Lawrence D'Oliveiro
Lawrence D'Oliveiro

Reputation: 2774

Just a note that the “new-style" vs “old-style” class distinction is specific to Python 2.x; in 3.x, all classes are “new-style”.

Upvotes: 3

unutbu
unutbu

Reputation: 879331

In Python2 this declares Table to be a new-style class (as opposed to "classic" class). In Python3 all classes are new-style classes, so this is no longer necessary.

New style classes have a few special attributes that classic classes lack.

class Classic: pass
class NewStyle(object): pass

print(dir(Classic))
# ['__doc__', '__module__']

print(dir(NewStyle))
# ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']

Also, properties and super do not work with classic classes.

In Python2 it is a good idea to make all classes new-style classes. (Though a lot of classes in the standard library are still classic classes, for the sake of backward-compatibility.)

In general, in a statement such as

class Foo(Base1, Base2):

Foo is being declared as a class inheriting from base classes Base1 and Base2.

object is the mother of all classes in Python. It is a new-style class, so inheriting from object makes Table a new-style class.

Upvotes: 152

Devraj
Devraj

Reputation: 3065

class Table and class Table(object) are no different for Python.

It's not a parameter, its extending from object (which is base Class like many other languages).

All it says is that it inherits whatever is defined in "object". This is the default behaviour.

Upvotes: 4

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