super

问题 I have created custom exception in python 3 and the over all code works just fine. But there is one thing I am not able to wrap my head around is that why do I need to send my message to the Exception class's __init__() and how does it convert the Custom exception into that string message when I try to print the exception since the code in the Exception or even the BaseException does not do much. Not quite able to understand why call the super().__init__() from custom exception? 回答1: This is

问题 This question already has answers here : In Java super.getClass() prints “Child” not “Parent” - why is that? (3 answers) Closed 3 years ago . Could you help me understand what gets printed in the code below System.out.println(super.getClass().getName()); ? I see "PrintSubClass3" printed, even when I have mentioned super . class PrintClass { int x = 0; int y = 1; void printMe() { System.out.println("X is " + x + ", Y is " + y); System.out.println("I am an instance of the class " +super

问题 This question already has answers here : In Java super.getClass() prints “Child” not “Parent” - why is that? (3 answers) Closed 3 years ago . Could you help me understand what gets printed in the code below System.out.println(super.getClass().getName()); ? I see "PrintSubClass3" printed, even when I have mentioned super . class PrintClass { int x = 0; int y = 1; void printMe() { System.out.println("X is " + x + ", Y is " + y); System.out.println("I am an instance of the class " +super

问题 As far as i know, super() is used to call the methods overwritten in the subclass (like an overwritten __init__ in the subclass). Also, i know that all python classes inherit from a special class called object . While studying OOP i ran into a weird example: class A(object): def __init__(self): print('A.__init__') super().__init__() class B(object): def __init__(self): print('B.__init__') super().__init__() class C(A, B): def __init__(self): print('C.__init__') super().__init__() I understand

问题 I have base class Foo with method spam and class Bar which overrides spam . I need to call spam of base class in method of some callback object which is defined in-place: public class Foo { public void spam() { // ... } } public class Bar extends Foo { @Override public void spam() { objectWhichRequireCallback(new Callback { @Override public void onCallback() { super.spam(); } }); } } This code is not working because super is related to Callback , not Bar class. Is it possible to call super

问题 This question already has answers here : Is it unnecessary to put super() in constructor? (6 answers) Closed 6 years ago . I always thought that when creating an object with a sub-class, we need to explicitly use super(arguments list) to call the constructor of the super class. However I did an experiment and realize that even without using the super() , the super class's constructor will be called automatically. Is this true? If this is true, when is super() redundant and when it is not?

问题 Im using code from Scrapy documentation, with "Product" class item created from scrapy.exporter import XmlItemExporter class ProductXmlExporter(XmlItemExporter): def serialize_field(self, field, name, value): if field == 'price': return f'$ {str(value)}' return super(Product, self).serialize_field(field, name, value) and always get error from command line return super(Product, self).serialize_field(field, name, value) TypeError: super(Product, obj): obj must be an instance or subtype of type

问题 I am new to python. I am trying to understand super() functionality in python multiple inheritance. class B(): def __init__(self): print("__init__ of B called") self.b = "B" class C(): def __init__(self): print("__init__ of C called") self.c = "C" class D(B, C): def __init__(self): print("__init__ of D called") super().__init__() def output(self): print(self.b, self.c) d = D() d.output() I am getting the following error: AttributeError: 'D' object has no attribute 'c' 回答1: super() will find

问题 A use case of the super() builtin in python is to call an overridden method. Here is a simple example of using super() to call Parent class's echo function: class Parent(): def echo(self): print("in Parent") class Child(Parent): def echo(self): super().echo() print("in Child") I've seen code that passes 2 parameters to super() . In that case, the signature looks somehing like super(subClass, instance) where subClass is the sub class calling super() from, and instance is the instance the call

问题 I'm trying to duplicate and then modify a class programmatically but I'm running into problems with python 3's magic super for example the following class Base(): def __init__(self): print("Base init") class Orginal(Base): def __init__(self): super().__init__() print("Orginal init") Modified = type(Orginal.__name__, Orginal.__bases__, dict(Orginal.__dict__)) Modified.f = lambda self: print("f") m = Modified() raises TypeError: super(type, obj): obj must be an instance or subtype of type So I