Dear All,
Summary of the question:
Is it generally safe to dynamically change an objects class; if not
under which conditions can it be considered safe.
Context:
Given the code below, I have no direct control over Base and M1. M1
is a instantiated by 'calling' the read-only property of Base.
I would like to transparently switch behaviour from M1 to M2. I have
tried several things, but finally settled on the code below. Although
it works really well, I am not sure whether I am about to shoot myself
in the foot. In short, what I do is derive from Base, shadow the read-only
property 'my_prop' so it returns M2 and finally replace an objects __class__
attribute with my derived class.
Any thoughts or comments?
(code below is Python 3)
class M1(object):
def __init__(self):
print('Initializing M1')
class M2(object):
def __init__(self):
print('Initializing M2')
class Base(object):
@property
def my_prop(self):
return M1()
class ShadowBase(Base):
@property
def my_prop(self):
return M2()
if __name__ == '__main__':
o = Base()
o.my_prop
# Prints 'Initializing M1'
o = Base()
o.__class__ = ShadowBase
o.my_prop
# Prints 'Initializing M2'
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