python's OOP question

[neoedmund]

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?

 
class C1(object):
def v(self, o):
return "expected "+o
 
class C2(object):
def v(self, o):
return "unexpected "+o
def m(self):
print self.v("aaa")
 
class C3(object):
def nothing(self):
pass
 
def test1():
o = C3()
setattr(o,"m",C2().m)
setattr(o,"v",C1().v)
o.m()
 
test1()
 
 

[Kay Schluehr]

neoedmund wrote:

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?

class C1(object):
    def v(self, o):
        return "expected "+o

class C2(object):
    def v(self, o):
        return "unexpected "+o
    def m(self):
        print self.v("aaa")

class C3(object):
    def nothing(self):
        pass

def test1():
    o = C3()
    setattr(o,"m",C2().m)
    setattr(o,"v",C1().v)
    o.m()

test1()

 

class C3(C1, C2):pass

>>C3.mro() # shows method resolution order

[<class '__main__.C3'>, <class '__main__.C1'>, <class '__main__.C2'>,
<type 'object'>]

>>o = C3()
o.m()

expected aaa

[Ben Finney]

"neoedmund" <ne*******@gmai l.comwrites:

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?

[code]

class C1(object):
def v(self, o):
return "expected "+o

class C2(object):
def v(self, o):
return "unexpected "+o
def m(self):
print self.v("aaa")

class C3(object):
def nothing(self):
pass

def test1():
o = C3()
setattr(o,"m",C 2().m)
setattr(o,"v",C 1().v)
o.m()

Setting attributes on an object externally isn't the same thing as
making bound methods of that object.

In this case, 'o.m' is a bound method of a C2 instance, and has no
knowledge of C1. 'o.v' is a bound method of a C1 instance, and has no
knowledge of C2. Neither of them has any knowledge of C3.

What is it you're trying to achieve?

--
\ "Unix is an operating system, OS/2 is half an operating system, |
`\ Windows is a shell, and DOS is a boot partition virus." -- |
_o__) Peter H. Coffin |
Ben Finney

[neoedmund]

thank you, Kay.

But i need a "dynamic" way. Say i have a existing class, and add some
method from other class into it.
Kay Schluehr wrote:

neoedmund wrote:

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?

 
 class C1(object):
     def v(self, o):
         return "expected "+o
 
 class C2(object):
     def v(self, o):
         return "unexpected "+o
     def m(self):
         print self.v("aaa")
 
 class C3(object):
     def nothing(self):
         pass
 
 def test1():
     o = C3()
     setattr(o,"m",C2().m)
     setattr(o,"v",C1().v)
     o.m()
 
 test1()
 
 

class C3(C1, C2):pass

>C3.mro() # shows method resolution order

[<class '__main__.C3'>, <class '__main__.C1'>, <class '__main__.C2'>,
<type 'object'>]

>o = C3()
o.m()

expected aaa

[neoedmund]

I'm trying to achieve a higher level of "reusabilit y". Maybe it cannot
be done in python? Can anybody help me？
Ben Finney wrote:

"neoedmund" <ne*******@gmai l.comwrites:

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?

[code]

class C1(object):
def v(self, o):
return "expected "+o

class C2(object):
def v(self, o):
return "unexpected "+o
def m(self):
print self.v("aaa")

class C3(object):
def nothing(self):
pass

def test1():
o = C3()
setattr(o,"m",C 2().m)
setattr(o,"v",C 1().v)
o.m()

Setting attributes on an object externally isn't the same thing as
making bound methods of that object.

In this case, 'o.m' is a bound method of a C2 instance, and has no
knowledge of C1. 'o.v' is a bound method of a C1 instance, and has no
knowledge of C2. Neither of them has any knowledge of C3.

What is it you're trying to achieve?

--
\ "Unix is an operating system, OS/2 is half an operating system, |
`\ Windows is a shell, and DOS is a boot partition virus." -- |
_o__) Peter H. Coffin |
Ben Finney

[Ben Finney]

[Please don't top-post above the text to which you're replying.]

"neoedmund" <ne*******@gmai l.comwrites:

I'm trying to achieve a higher level of "reusabilit y". Maybe it
cannot be done in python? Can anybody help me？

What, specifically, are you trying to achieve? What problem needs
solving?

--
\ "If you're a horse, and someone gets on you, and falls off, and |
`\ then gets right back on you, I think you should buck him off |
_o__) right away." -- Jack Handey |
Ben Finney

[neoedmund]

python use multiple inheritance.
but "inheritanc e" means you must inherite all methods from super type.
now i just need "some" methods from one type and "some" methods from
other types,
to build the new type.
Do you think this way is more flexible than tranditional inheritance?
Ben Finney wrote:

[Please don't top-post above the text to which you're replying.]

"neoedmund" <ne*******@gmai l.comwrites:

I'm trying to achieve a higher level of "reusabilit y". Maybe it
cannot be done in python? Can anybody help me？

What, specifically, are you trying to achieve? What problem needs
solving?

--
\ "If you're a horse, and someone gets on you, and falls off, and |
`\ then gets right back on you, I think you should buck him off |
_o__) right away." -- Jack Handey |
Ben Finney

[Gregor Horvath]

neoedmund schrieb:

python use multiple inheritance.
but "inheritanc e" means you must inherite all methods from super type.
now i just need "some" methods from one type and "some" methods from
other types,
to build the new type.
Do you think this way is more flexible than tranditional inheritance?

Probably your problem is better solved with delegation instead of
inheritance.

--
Servus, Gregor

[George Sakkis]

neoedmund wrote:

python use multiple inheritance.
but "inheritanc e" means you must inherite all methods from super type.
now i just need "some" methods from one type and "some" methods from
other types,
to build the new type.
Do you think this way is more flexible than tranditional inheritance?

The following does the trick:

from types import MethodType

def addMethod(meth, obj):
f = meth.im_func
setattr(obj, f.__name__, MethodType(f,ob j))

def test1():
addMethod(C2.m, C3)
addMethod(C1.v, C3)
o = C3()
o.m()

The same works as is on modifying individual instances, rather than
their class:

def test2():
o = C3()
addMethod(C2.m, o)
addMethod(C1.v, o)
o.m()
# raises AttributeError
# C3().m()
George

[neoedmund]

I found a dynamic way to inherite classes:

def MixIn(pyClass, mixInClass):
if mixInClass not in pyClass.__bases __:
pyClass.__bases __ += (mixInClass,)

def test1():
o = C3()
MixIn(C3,C1)
MixIn(C3,C2)
o.m()

"expected aaa"

neoedmund wrote:

thank you, Kay.

But i need a "dynamic" way. Say i have a existing class, and add some
method from other class into it.
Kay Schluehr wrote:

neoedmund wrote:

There's a program, it's result is "unexpected aaa", i want it to be
"expected aaa". how to make it work?
>

 >
 class C1(object):
     def v(self, o):
         return "expected "+o
 >
 class C2(object):
     def v(self, o):
         return "unexpected "+o
     def m(self):
         print self.v("aaa")
 >
 class C3(object):
     def nothing(self):
         pass
 >
 def test1():
     o = C3()
     setattr(o,"m",C2().m)
     setattr(o,"v",C1().v)
     o.m()
 >
 test1()
 >
 

class C3(C1, C2):pass

>>C3.mro() # shows method resolution order

[<class '__main__.C3'>, <class '__main__.C1'>, <class '__main__.C2'>,
<type 'object'>]

>>o = C3()
>>o.m()

expected aaa