method-resolution-order

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, **kw): print("Car.__init__()") super(Car,self).__init__(*a, **kw) if __name__ == '__main__': c = Car()

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.PYQT_VERSION_STR) f = Foo() a) When class Foo inherits from QtCore.QObject and Bar we get: (<class '_

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.new.do-it; put '-' x 10; Bar.new.do-it: 1; Bar.new.do-it: 'Perl 6'; Bar.new.do-it: <1/137>; Bar.new.do

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 a server where A and B will be plugins that are loaded on startup. These are residing in their own

class MyClass(object): pass print MyClass.__mro__ print dir(MyClass) Output: (<class '__main__.MyClass'>, <type 'object'>) ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__'] Why is __mro__ not listed with dir() ? From the Python documentation: Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply an interesting set of names more than it tries

I am trying to understand MRO in Python. Although there are various posts here, I am not particularly getting what I want. Consider two classes A and B derived from BaseClass , each having an __init__ taking different params. class BaseClass(object): def __init__(self): print "I am the base class" class A(BaseClass): def __init__(self, something, anotherthing): super(A, self).__init__() self.something = something self.anotherthing = anotherthing def methodsA(self): ... class B(BaseClass): def __init__(self, someOtherThing): super(B, self).__init__() self.someOtherThing = someOtherThing def