Dynamically adding methods to objects?

[damian birchler]

Hello there!

I'm wondering if it is possible to automatically dynamically add
methods to a class instance. For example, if there is a class Foo with
one method named
add_function and an instance of Foo f -

class Foo:
add_function(self, name, args):
# ...
# ...

f = Foo()

-, could one add arbitrary methods to f calling its method
add_function?

I know how to do it manually, I just define a function and assigne it
to f -

def bar():
pass

f.bar = bar -,
but what if this should be done at runtime. How can I get the string
passed to f.add_function as name to be the name of a new function in
the function's definiton?

Thanks a lot

[Holger Türk]

damian birchler wrote:

I know how to do it manually, I just define a function and assigne it
to f -

def bar():
pass

f.bar = bar -,
but what if this should be done at runtime. How can I get the string
passed to f.add_function as name to be the name of a new function in
the function's definiton?

f.bar = bar is the same as setattr (f, "bar", bar)

Remember that bar does not become a method of f, but remains
only a function which is stored in f. Is not subject of the
binding of the "self" parameter.

Greetings,

Holger

[John Roth]

"Holger Türk" <ht**@gmx.de> wrote in message
news:c9*************@news.t-online.com...

damian birchler wrote:

I know how to do it manually, I just define a function and assigne it
to f -

def bar():
pass

f.bar = bar -,
but what if this should be done at runtime. How can I get the string
passed to f.add_function as name to be the name of a new function in
the function's definiton?
f.bar = bar is the same as setattr (f, "bar", bar)

Remember that bar does not become a method of f, but remains
only a function which is stored in f. Is not subject of the
binding of the "self" parameter.

Ah, but that's what I want to do - have a ***method***
where the self parameter works the way I expect it to.

John Roth
Greetings,

Holger

[Carl Banks]

John Roth wrote:

"Holger T?rk" <ht**@gmx.de> wrote in message
news:c9*************@news.t-online.com...

damian birchler wrote:

> I know how to do it manually, I just define a function and assigne it
> to f -
>
> def bar():
> pass
>
> f.bar = bar -,
> but what if this should be done at runtime. How can I get the string
> passed to f.add_function as name to be the name of a new function in
> the function's definiton?

f.bar = bar is the same as setattr (f, "bar", bar)

Remember that bar does not become a method of f, but remains
only a function which is stored in f. Is not subject of the
binding of the "self" parameter.

Ah, but that's what I want to do - have a ***method***
where the self parameter works the way I expect it to.

Is this what you want?

def selfize(obj,func):
def callfunc(*args,**kwargs):
func(obj,*args,**kwargs)
return callfunc

f.bar = withself(f,bar)
--
CARL BANKS http://www.aerojockey.com/software
"If you believe in yourself, drink your school, stay on drugs, and
don't do milk, you can get work."
-- Parody of Mr. T from a Robert Smigel Cartoon

[Leif K-Brooks]

damian birchler wrote:

I'm wondering if it is possible to automatically dynamically add
methods to a class instance.

Try something like this:

import new

class Foo(object):
def add_method(self, name, prints):
"""Add a method to the class which prints a string.

Arguments:
name - the name of the method
prints - the string the method should print
"""
def method(self):
print prints

method = new.instancemethod(method, self, Foo)
setattr(self, name, method)

instance = Foo()
instance.add_method('foo', 'I am foo. Fear me!')
instance.add_method('bar', "I am the humble bar. Please don't hurt me.")
instance.foo()
instance.bar()

[Jacek Generowicz]

Carl Banks <im*****@aerojockey.invalid> writes:

John Roth wrote:

"Holger T?rk" <ht**@gmx.de> wrote in message
news:c9*************@news.t-online.com...

damian birchler wrote:
[ f = Foo() ]
> I know how to do it manually, I just define a function and assigne it
> to f -
>
> def bar():
> pass
>
> f.bar = bar -,
> but what if this should be done at runtime. How can I get the string
> passed to f.add_function as name to be the name of a new function in
> the function's definiton?

f.bar = bar is the same as setattr (f, "bar", bar)

Remember that bar does not become a method of f, but remains
only a function which is stored in f. Is not subject of the
binding of the "self" parameter.

Ah, but that's what I want to do - have a ***method***
where the self parameter works the way I expect it to.

Is this what you want?

def selfize(obj,func):
def callfunc(*args,**kwargs):
func(obj,*args,**kwargs)
return callfunc

f.bar = withself(f,bar)

What's "withself" ?

Isn't John saying he wants exactly what the instancemethod function in
the new module was designed for:

import new
f.bar = new.instancemethod(bar, f, Foo)
?