Is it possible to access Methods of a class without creating object?

[psbasha]

HI,

Is it possible to access the Methods of a class without creating object?


Thanks
PSB

[bartonc]

HI,

Is it possible to access the Methods of a class without creating object?


Thanks
PSB

The Python Manuals says:
Class instance methods are either bound or unbound, referring to whether the method was accessed through an instance or a class, respectively. When a method is unbound, its im_self attribute will be None and if called, an explicit self object must be passed as the first argument. In this case, self must be an instance of the unbound method's class (or a subclass of that class), otherwise a TypeError is raised.

in section 2.3.10 Other Built-in Types sub 2.3.10.4 Methods (version 2.4.4)

[bvdet]

HI,

Is it possible to access the Methods of a class without creating object?


Thanks
PSB

You can access class methods without creating a class instance.

class Point(object):
    def __init__(self, x=0.0, y=0.0, z=0.0):
        self.x = float(x)
        self.y = float(y)
        self.z = float(z)
    def test(cls):
        print 'You can access a class method without creating an instance.'
    test = classmethod(test)

>>> Point.test()
You can access a class method without creating an instance.
>>>
In Python 2.4, class methods can be created with the @classmethod decorator.

[bartonc]

You can access class methods without creating a class instance.

class Point(object):
    def __init__(self, x=0.0, y=0.0, z=0.0):
        self.x = float(x)
        self.y = float(y)
        self.z = float(z)
    def test(cls):
        print 'You can access a class method without creating an instance.'
    test = classmethod(test)

>>> Point.test()
You can access a class method without creating an instance.
>>>
In Python 2.4, class methods can be created with the @classmethod decorator.

True. But doesn't this negate the reason for having an object in the first place? Without access to self.anyThing, test() should be refactored into a different (module, perhaps) scope.

[bvdet]

True. But doesn't this negate the reason for having an object in the first place? Without access to self.anyThing, test() should be refactored into a different (module, perhaps) scope.

I agree. I have never needed a class method without an instance.

[psbasha]

Thanks for the reply.

This helps us when we dont want to create the object of the class and make use of everywhere (helpful in creating a MathUtil module).I hope this functionality is similar to using a static functions in a class or namespace methods in C++.

Static function:
------------------------
class Sample{

public :

static void Func1(){}

};

void main(){

Sample::Func1();
}

Namespace:
------------------------
namespace Sample1{

public :

void Func1(){}

};

void main(){

Sample1::Func1();
}

-PSB

[psbasha]

If I want to access all the Methods of the classes ,so I have to define all the methods similar to " test = classmethod(test)"

class X:

def Func1():
print "Func1()"

def Func2():
print "Func2()"

.............
def Funcn():
print "Funcn()"

Func1= classmethod(Func1)
Func2= classmethod(Func2)

.....

Funcn= classmethod(Funcn)

-PSB

[bvdet]

If I want to access all the Methods of the classes ,so I have to define all the methods similar to " test = classmethod(test)"

class X:

def Func1():
print "Func1()"

def Func2():
print "Func2()"

.............
def Funcn():
print "Funcn()"

Func1= classmethod(Func1)
Func2= classmethod(Func2)

.....

Funcn= classmethod(Funcn)

-PSB

If you use Python 2.4 or higher, use decorators:

    @classmethod
    def Funcn():
        print "Funcn()"

Why can't you use code tags?

[bvdet]

If you use Python 2.4 or higher, use decorators:

    @classmethod
    def Funcn():
        print "Funcn()"

Why can't you use code tags?

I failed to mention that the class object is passed to a class method, so you must have an argument in the argument list. By convention, the name of this argument is cls.

    @classmethod
    def Funcn(cls):
        print "Funcn()"

You may want to use static methods instead:

class Point(object):
    def __init__(self, x=0.0, y=0.0, z=0.0):
        self.x = float(x)
        self.y = float(y)
        self.z = float(z)
    def test(cls):
        print 'You can access a class method without creating an instance.'
    test = classmethod(test)
    def test2():
        print 'I have never used a static method.'
    test2 = staticmethod(test2)

>>> Point.test2()
I have never used a static method.
>>> Point.test()
You can access a class method without creating an instance.
>>> 

[psbasha]

Thanks for the reply.

Here both are performing the same functionality "accessing the methods of a class without creating the object".Then why two.

Is there anything different in memory management of it?.

Thanks
PSB

[bvdet]

Thanks for the reply.

Here both are performing the same functionality "accessing the methods of a class without creating the object".Then why two.

Is there anything different in memory management of it?.

Thanks
PSB

Not that I am aware of, except the class method receives the class object as an argument.