method-resolution-order

问题 In the documentation on the Python webpage the method resolution order for classic classes in python is described as a depth-first left-to-right search. I tried to test this with this piece of code: class A(object): def __init__(self): print "Initialized A" class B(A): def test(): print "Initialized B" class C(A): def __init__(self): print "Initialized C" class D(B, C): def __init__(self): super(D, self).__init__() print "Initialized D" When I create an instance of object D: D() I get the

问题 There is a simple program in python3: from PyQt4 import QtCore import PyQt4 class Bar(object): def __init__(self): print("Bar start") super(Bar, self).__init__() print("Bar end") class FakeQObject(object): def __init__(self): print("FakeQObject start") super(FakeQObject, self).__init__() print("FakeQObject end") class Foo(QtCore.QObject, Bar): #class Foo(FakeQObject, Bar): def __init__(self): print("Foo start") super(Foo, self).__init__() print("Foo end") print(Foo.__mro__) print(PyQt4.QtCore

问题 Consider this example where a subclass has a multi method with no signature and one with a slurpy parameter: class Foo { multi method do-it { put "Default" } multi method do-it ( Int $n ) { put "Int method" } multi method do-it ( Str $s ) { put "Str method" } multi method do-it ( Rat $r ) { put "Rat method" } } class Bar is Foo { multi method do-it { put "Bar method" } multi method do-it (*@a) { put "Bar slurpy method" } } Foo.new.do-it: 1; Foo.new.do-it: 'Perl 6'; Foo.new.do-it: <1/137>; Foo

问题 Consider the following class hierarchy: base class Object with a virtual method foo() an arbitrary hierarchy with multiple inheritance (virtual and non-virtual); each class is a subtype of Object; some of them override foo(), some don't a class X from this hierarchy, not overriding foo() How to determine which method will be executed upon a call of foo() on an object of class X in C++? (I'm looking for the algorithm, not any specific case.) 回答1: There is no MRO in C++ like Python. If a method

问题 The following program can run successfully: class Simple(object): def __init__(self, name): self.name = name def __add__(self, other): c = Composite() c._members.append(self) c._members.append(other) return c def __repr__(self): return "Simple('%s')" % self.name class Composite(object): def __init__(self): self._members = [] def __add__(self, obj): if isinstance(obj, Simple): out = Composite() out._members = [k for k in self._members] + [obj] elif isinstance(obj, Composite): out = Composite()

问题 My situation is this: public class InheritedClass : BaseClass { public override void SomeMethod() { AnotherMethod(); } public override void AnotherMethod() { } } public class BaseClass { public virtual void SomeMethod() { } public virtual void AnotherMethod() { } } So which method is called when I call InheritedClassInstance.SomeMethod ? Does it call InheritedClassInstance.AnotherMethod , or the BaseClass's AnotherMethod ? 回答1: It calls InheritedClassInstance.AnotherMethod() If you wanted it

问题 I stumbled across this extra, no-underscores mro method when I was using __metaclass__ = abc.ABCMeta . It seems to be the same as __mro__ except that it returns a list instead of a tuple. Here's a random example (ideone snippet): import abc import copy class Life(object): __metaclass__ = abc.ABCMeta @abc.abstractmethod def reproduce(self): pass class Bacterium(Life): def reproduce(self): return copy.deepcopy(self) wiggly = Bacterium() print wiggly.__class__.__mro__ # (<class '__main__

问题 Today i was trying to figure out how __mro__ and super works in python, I found something interesting as well as strange to me, because I got something which is not that i understood after reading __mro__ . Here is the code snippets. Code Snippets 1: #!/usr/bin/pyhon class A(object): def test(self): return 'A' class B(A): def test(self): return 'B to %s' % super(B, self).test() class C(A): def test(self): return 'C' class D(B, C): pass print D().test() Output : B to C Code snippet 2: When I

问题 Say I have a class A , B and C . Class A and B are both mixin classes for Class C . class A( object ): pass class B( object ): pass class C( object, A, B ): pass This will not work when instantiating class C. I would have to remove object from class C to make it work. (Else you'll get MRO problems). TypeError: Error when calling the metaclass bases Cannot create a consistent method resolution order (MRO) for bases B, object, A However, my case is a bit more complicated. In my case class C is

问题 I'm really confused by the following code sample: class Meta_1(type): def __call__(cls, *a, **kw): # line 1 print("entering Meta_1.__call__()") print(cls) # line 4 print(cls.mro()) # line 5 print(super(Meta_1, cls).__self__) # line 6 rv = super(Meta_1, cls).__call__(*a, **kw) # line 7 print("exiting Meta_1.__call__()") return rv class Car(object, metaclass=Meta_1): def __new__(cls, *a, **kw): print("Car.__new__()") rv = super(Car, cls).__new__(cls, *a, **kw) return rv def __init__(self, *a, *