Adding methods from one class to another, dynamically

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From: Oltmans on 1 Feb 2010 15:06

---

Hello Python gurus,

I'm quite new when it comes to Python so I will appreciate any help.
Here is what I'm trying to do. I've two classes like below

import new
import unittest

class test(unittest.TestCase):
def test_first(self):
print 'first test'
def test_second(self):
print 'second test'
def test_third(self):
print 'third test'

class tee(unittest.TestCase):
pass

and I want to attach all test methods of 'test'(i.e. test_first(),
test_second() and test_third()) class to 'tee' class. So I'm trying to
do something like

if __name__=="__main__":
for name,func in inspect.getmembers(test,inspect.ismethod):
if name.find('test_')!= -1:
tee.name = new.instancemethod(func,None,tee)

after doing above when I run this statement
print dirs(tee)
I don't see test_first(), test_second() and test_third() attached to
class 'tee'. Any ideas, on how can I attach methods of class 'test' to
class 'tee' dynamically? Any help is highly appreciated.

Many thanks and I look forward to any help.

From: Chris Rebert on 1 Feb 2010 15:25

---

On Mon, Feb 1, 2010 at 12:06 PM, Oltmans <rolf.oltmans(a)gmail.com> wrote:
> Hello Python gurus,
>
> I'm quite new when it comes to Python so I will appreciate any help.
> Here is what I'm trying to do. I've two classes like below
>
> import new
> import unittest
>
> class test(unittest.TestCase):
>    def test_first(self):
>        print 'first test'
>    def test_second(self):
>        print 'second test'
>    def test_third(self):
>        print 'third test'
>
> class tee(unittest.TestCase):
>    pass
>
> and I want to attach all test methods of 'test'(i.e. test_first(),
> test_second() and test_third()) class to 'tee' class. So I'm trying to
> do something like
>
> if __name__=="__main__":
>    for name,func in inspect.getmembers(test,inspect.ismethod):
>        if name.find('test_')!= -1:
>            tee.name = new.instancemethod(func,None,tee)

This ends up repeatedly assigning to the attribute "name" of tee; if
you check dir(tee), you'll see the string "name" as an entry. It does
*not* assign to the attribute named by the string in the variable
`name`.
You want setattr(): http://docs.python.org/library/functions.html#setattr
Assuming the rest of your code chunk is correct:

setattr(tee, name, new.instancemethod(func,None,tee))

Cheers,
Chris
--
http://blog.rebertia.com

From: Carl Banks on 1 Feb 2010 15:45

---

On Feb 1, 12:06 pm, Oltmans <rolf.oltm...(a)gmail.com> wrote:
> Hello Python gurus,
>
> I'm quite new when it comes to Python so I will appreciate any help.
> Here is what I'm trying to do. I've two classes like below
>
> import new
> import unittest
>
> class test(unittest.TestCase):
>     def test_first(self):
>         print 'first test'
>     def test_second(self):
>         print 'second test'
>     def test_third(self):
>         print 'third test'
>
> class tee(unittest.TestCase):
>     pass
>
> and I want to attach all test methods of 'test'(i.e. test_first(),
> test_second() and test_third()) class to 'tee' class.


Simplest way:

class tee(test):
pass


To do it dynamically the following might work:

class tee(unittest.TestCase):
pass

tee.__bases__ = (test,)
tee.__bases__ = (test2,) # dynamically reassign base


> So I'm trying to
> do something like
>
> if __name__=="__main__":
>     for name,func in inspect.getmembers(test,inspect.ismethod):
>         if name.find('test_')!= -1:
>             tee.name = new.instancemethod(func,None,tee)
>
> after doing above when I run this statement
> print dirs(tee)
> I don't see test_first(), test_second() and test_third() attached to
> class 'tee'. Any ideas, on how can I attach methods of class 'test' to
> class 'tee' dynamically? Any help is highly appreciated.

If you want to do it this way--and I recommend regular inheritance if
you can--this is how:

for x in dir(test): # or inspect.getmembers
if x.startswith('test_'):
method = getattr(test,x)
function = method.im_func
setattr(tee,x,function)

The business with method.im_func is because in Python 2.x the getattr
on a class will actually returns an unbound method, so you have to get
at the actual function object with im_func. In Python 3 this is not
necessary.

Carl Banks

From: Gerald Britton on 1 Feb 2010 15:50

---

Or you could just do a mixin:

tee.__class__.__bases__ = (test,) + tee.__class__.__bases__


On Mon, Feb 1, 2010 at 3:25 PM, Chris Rebert <clp2(a)rebertia.com> wrote:
> On Mon, Feb 1, 2010 at 12:06 PM, Oltmans <rolf.oltmans(a)gmail.com> wrote:
>> Hello Python gurus,
>>
>> I'm quite new when it comes to Python so I will appreciate any help.
>> Here is what I'm trying to do. I've two classes like below
>>
>> import new
>> import unittest
>>
>> class test(unittest.TestCase):
>>    def test_first(self):
>>        print 'first test'
>>    def test_second(self):
>>        print 'second test'
>>    def test_third(self):
>>        print 'third test'
>>
>> class tee(unittest.TestCase):
>>    pass
>>
>> and I want to attach all test methods of 'test'(i.e. test_first(),
>> test_second() and test_third()) class to 'tee' class. So I'm trying to
>> do something like
>>
>> if __name__=="__main__":
>>    for name,func in inspect.getmembers(test,inspect.ismethod):
>>        if name.find('test_')!= -1:
>>            tee.name = new.instancemethod(func,None,tee)
>
> This ends up repeatedly assigning to the attribute "name" of tee; if
> you check dir(tee), you'll see the string "name" as an entry. It does
> *not* assign to the attribute named by the string in the variable
> `name`.
> You want setattr(): http://docs.python.org/library/functions.html#setattr
> Assuming the rest of your code chunk is correct:
>
> setattr(tee, name, new.instancemethod(func,None,tee))
>
> Cheers,
> Chris
> --
> http://blog.rebertia.com
> --
> http://mail.python.org/mailman/listinfo/python-list
>



--
Gerald Britton

From: Oltmans on 1 Feb 2010 15:55

---

Thank you for your help, Chris. Looks like I can now attach methods to
class 'tee'. However, after attaching methods to 'tee' when I try to
run them using suite.run() I don't see any of the methods running, I'm
sorry but I've no clue what's failing this. Any insights will be
highly appreciated. Here is the sample code
filename: check.py
---
import inspect
import unittest


class result(unittest.TestResult):

def addSuccess(self,test):
print str(test) + ' succeeded'
def addError(self,test,err):
print 'An error occured while running the test ' + str(test) +
' and error is = ' + str(err)
def addFailure(self,test,err):
print str(test) + " failed with an error =" + str(err)



class test(unittest.TestCase):
def test_first(self):
print 'first test'
def test_second(self):
print 'second test'
def test_third(self):
print 'third test'

import new
class tee(unittest.TestCase):
pass

if __name__=="__main__":
r = result()
for name,func in inspect.getmembers(test,inspect.ismethod):
if name.find('test_')!= -1:

setattr(tee, name, new.instancemethod(func,None,tee))

suite = unittest.defaultTestLoader.loadTestsFromName('check.tee')
suite.run(r)
---

Then line suite.run(r) should have run the methods that we just
attached, but it's not. I must be missing something here. Please
enlighten me.

Thanks.
On Feb 2, 1:25 am, Chris Rebert <c...(a)rebertia.com> wrote:
> On Mon, Feb 1, 2010 at 12:06 PM, Oltmans <rolf.oltm...(a)gmail.com> wrote:
> > Hello Python gurus,
>
> > I'm quite new when it comes to Python so I will appreciate any help.
> > Here is what I'm trying to do. I've two classes like below
>
> > import new
> > import unittest
>
> > class test(unittest.TestCase):
> >    def test_first(self):
> >        print 'first test'
> >    def test_second(self):
> >        print 'second test'
> >    def test_third(self):
> >        print 'third test'
>
> > class tee(unittest.TestCase):
> >    pass
>
> > and I want to attach all test methods of 'test'(i.e. test_first(),
> > test_second() and test_third()) class to 'tee' class. So I'm trying to
> > do something like
>
> > if __name__=="__main__":
> >    for name,func in inspect.getmembers(test,inspect.ismethod):
> >        if name.find('test_')!= -1:
> >            tee.name = new.instancemethod(func,None,tee)
>
> This ends up repeatedly assigning to the attribute "name" of tee; if
> you check dir(tee), you'll see the string "name" as an entry. It does
> *not* assign to the attribute named by the string in the variable
> `name`.
> You want setattr():http://docs.python.org/library/functions.html#setattr
> Assuming the rest of your code chunk is correct:
>
> setattr(tee, name, new.instancemethod(func,None,tee))
>
> Cheers,
> Chris
> --http://blog.rebertia.com- Hide quoted text -
>
> - Show quoted text -

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