Python using derived class's method in parent class?
Can I force a parent class to call a derived class's version of a function?
class Base(object):
attr1 = ''
attr2 = ''
def virtual(self):
pass # doesn't do anything in the parent class
def func(self):
print "%s, %s" % (开发者_运维技巧self.attr1, self.attr2)
self.virtual()
and a class that derives from it
class Derived(Base):
attr1 = 'I am in class Derived'
attr2 = 'blah blah'
def virtual(self):
# do stuff...
# do stuff...
Clearing up vagueness:
d = Derived()
d.func() # calls self.virtual() which is Base::virtual(),
# and I need it to be Derived::virtual()
If you instantiate a Derived
(say d = Derived()
), the .virtual
that's called by d.func()
is Derived.virtual
. If there is no instance of Derived
involved, then there's no suitable self
for Derived.virtual
and so of course it's impossible to call it.
It isn't impossible -- there is a way around this actually, and you don't have to pass in the function or anything like that. I am working on a project myself where this exact problem came up. Here is the solution:
class Base(): # no need to explicitly derive object for it to work
attr1 = 'I am in class Base'
attr2 = 'halb halb'
def virtual(self):
print "Base's Method"
def func(self):
print "%s, %s" % (self.attr1, self.attr2)
self.virtual()
class Derived(Base):
attr1 = 'I am in class Derived'
attr2 = 'blah blah'
def __init__(self):
# only way I've found so far is to edit the dict like this
Base.__dict__['_Base_virtual'] = self.virtual
def virtual(self):
print "Derived's Method"
if __name__ == '__main__':
d = Derived()
d.func()
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