Mixing classes...

[Ivan Voras]

Is this possible:

class C1:
def somemethods(self):
"""methods do stuff, create member variables"""
pass

def f1():
"""function returns instances of C1, somewhat manipulated into specific
states"""
return C1()
class C2(C1): # C2 derives from C1
def othermethods(self):
"""new methods are introduced, but no new member variables (they work
on existing ones)"""
pass

# So far, everything's ok. Now, i want to create instance of
# C1 using f1:

c = f1() # could be equal to "c=C1()", but not always...

# ... and somehow "add" or "overlay" the additional methods
# declared in C2 on the object "c". I tried this:

c.othermethods=C2.othermethods

c.othermethods() # fails here, is confused about what is 'self'
#######
While this is probably considered "strange", and it's certainly not good
design style, I somehow feel it could be possible to do in python. Any
clues?

[Hans Nowak]

Ivan Voras wrote:

Is this possible:

class C1:
def somemethods(self):
"""methods do stuff, create member variables"""
pass

def f1():
"""function returns instances of C1, somewhat manipulated into
specific states"""
return C1()
class C2(C1): # C2 derives from C1
def othermethods(self):
"""new methods are introduced, but no new member variables (they
work on existing ones)"""
pass

# So far, everything's ok. Now, i want to create instance of
# C1 using f1:

c = f1() # could be equal to "c=C1()", but not always...

# ... and somehow "add" or "overlay" the additional methods
# declared in C2 on the object "c". I tried this:

c.othermethods=C2.othermethods

c.othermethods() # fails here, is confused about what is 'self'
#######
While this is probably considered "strange", and it's certainly not good
design style, I somehow feel it could be possible to do in python. Any
clues?

Use new.instancemethod:

class C1: .... def somemethods(self):
.... print 'somemethods'
.... def f1(): .... return C1()
.... class C2(C1): .... def othermethods(self):
.... print 'othermethods'
.... c = f1()
c.somemethods() somemethods import new
c.othermethods = new.instancemethod(C2.othermethods.im_func, c, c.__class__)
c.othermethods()

othermethods

HTH,

--
Hans Nowak (ha**@zephyrfalcon.org)
http://zephyrfalcon.org/