use object method without initializing object

[Reckoner]

would it be possible to use one of an object's methods without
initializing the object?

In other words, if I have:

class Test:
def __init__(self):
print 'init'
def foo(self):
print 'foo'

and I want to use the foo function without hitting the
initialize constructor function.

Is this possible?

 

[colas.francis]

would it be possible to use one of an object's methods without
initializing the object?

In other words, if I have:

class Test:
def __init__(self):
print 'init'
def foo(self):
print 'foo'

and I want to use the foo function without hitting the
initialize constructor function.

Is this possible?

Yes:

In [214]: class Test:
.....: def foo(self):
.....: print 'foo'
.....:

In [215]: t = Test()

In [216]: t.foo()
foo

 

[Robert Bossy]

would it be possible to use one of an object's methods without
initializing the object?

In other words, if I have:

class Test:
def __init__(self):
print 'init'
def foo(self):
print 'foo'

and I want to use the foo function without hitting the
initialize constructor function.

Is this possible?

Hi,

Yes. It is possible and it is called "class method". That is to say, it
is a method bound to the class, and not to the class instances.
In pragmatic terms, class methods have three differences from instance
methods:
1) You have to declare a classmethod as a classmethod with the
classmethod() function, or the @classmethod decorator.
2) The first argument is not the instance but the class: to mark this
clearly, it is usually named cls, instead of self.
3) Classmethods are called with class objects, which looks like this:
ClassName.class_method_name(...).

In your example, this becomes:

class Test(object):
def __init__(self):
print 'init'
@classmethod
def foo(cls):
print 'foo'


Now call foo without instantiating a Test:
Test.foo()

RB

 

[colas.francis]

Hi,

Yes. It is possible and it is called "class method". That is to say, it
is a method bound to the class, and not to the class instances.
In pragmatic terms, class methods have three differences from instance
methods:
1) You have to declare a classmethod as a classmethod with the
classmethod() function, or the @classmethod decorator.
2) The first argument is not the instance but the class: to mark this
clearly, it is usually named cls, instead of self.
3) Classmethods are called with class objects, which looks like this:
ClassName.class_method_name(...).

In your example, this becomes:

class Test(object):
def __init__(self):
print 'init'
@classmethod
def foo(cls):
print 'foo'

Now call foo without instantiating a Test:
Test.foo()

To be complete, you can also define a static method that will not even
be passed the class as argument:

In [217]: class Test(object):
.....: def __init__(self):
.....: print 'init'
.....: @staticmethod
.....: def foo():
.....: print 'foo'
.....:

In [218]: Test.foo()
foo