python Python在父类中使用派生类的方法？
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Python using derived class's method in parent class?
提问by
Can I force a parent class to call a derived class's version of a function?
我可以强制父类调用派生类的函数版本吗？
class Base(object):
attr1 = ''
attr2 = ''
def virtual(self):
pass # doesn't do anything in the parent class
def func(self):
print "%s, %s" % (self.attr1, self.attr2)
self.virtual()
and a class that derives from it
和一个派生自它的类
class Derived(Base):
attr1 = 'I am in class Derived'
attr2 = 'blah blah'
def virtual(self):
# do stuff...
# do stuff...
Clearing up vagueness:
清除模糊：
d = Derived()
d.func() # calls self.virtual() which is Base::virtual(),
# and I need it to be Derived::virtual()
采纳答案by Alex Martelli
If you instantiate a Derived(say d = Derived()), the .virtualthat's called by d.func()isDerived.virtual. If there is no instance of Derivedinvolved, then there's no suitable selffor Derived.virtualand so of course it's impossible to call it.
如果您实例化 a Derived(say d = Derived())，则.virtual调用的d.func()是 isDerived.virtual。如果没有Derived涉及的实例，那么就没有合适self的Derived.virtual，所以当然不可能称之为。
回答by Jyaan
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:
这并非不可能——实际上有一种方法可以解决这个问题，而且您不必传入函数或类似的东西。我自己正在做一个项目，这个项目出现了这个确切的问题。这是解决方案：
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()
