If you really need to use the ID this way, use parameters:
class Parent(object):
def __init__(self, id):
self.id = id
class Child1(Parent):
_id_counter = count(0)
def __init__(self):
Parent.__init__(self, 100 + self._id_counter.next())
print 'Child1:', self.id
etc.
This assumes you won't be constructing instances of Parent directly, but that looks reasonable with your example code.
Top answer 1 of 3
10
If you really need to use the ID this way, use parameters:
class Parent(object):
def __init__(self, id):
self.id = id
class Child1(Parent):
_id_counter = count(0)
def __init__(self):
Parent.__init__(self, 100 + self._id_counter.next())
print 'Child1:', self.id
etc.
This assumes you won't be constructing instances of Parent directly, but that looks reasonable with your example code.
2 of 3
4
If you don't want to violate the DRY principle like falsetru suggests, you'll need to use metaclasses. I was thinking of writing something up, but there's already a good long description of metaclasses on SO, so check it out.
Metaclasses, in short, let you control subclass creation.
Basically, what you need to do is, upon the creation of a subclass of Parent, add the _id member to the newly-created subclass.
Python3
python3.info › advanced › oop-inheritance › override.html
4.5. Inheritance Override — Python - from None to AI
Child class will override parent's class variable · >>> class User: ... ROLE = 'user' >>> >>> class Admin(User): ... ROLE = 'admin' Using this class variable will use the child's field: >>> myaccount = Admin() >>> myaccount.ROLE 'admin' Instance variables are inherited as any other attribute ·
Cannot override class variable -- using `Final` and `ClassVar`
Bug Report PEP 591 indicates: Type checkers should infer a final attribute that is initialized in a class body as being a class variable. Variables should not be annotated with both ClassVar and Fi... More on github.com
2
July 6, 2023Changing Parent attributes through child class
I think i know what you want to do. I think you are trying to make a tree of objects where child objects can influence their parent objects. To do this you have to pass an instance of the parent into the child. Its easiest to do when creating it. class std_node(): def __init__(self,name,parent=None): self.name = name self.parent = parent # instantiate a parent p = std_node("parent") # instantiate a child c = std_node("child",p) # change parent name via child c.parent.name = "grand parent" More on reddit.com
3
1
February 10, 2023Confused about class variables, also with inheritance
The class variables and instance variables remain separate if an instance variable of the same name is created. One doesn't override the other, but the class variable will no longer be readable via the object: In [1]: class c: ...: a = 1 ...: def __init__(self): ...: self.a = 2 ...: In [2]: obj = c() In [3]: c.a Out[3]: 1 In [4]: obj.a Out[4]: 2 As for inheritance, yes if you assign a value to a class variable on a child that has the same name as one of the parent's class variables, then a separate class variable of that name will be created for the child. Again, the two will remain separate, one readable from the parent and one readable from the child, but the parent's variable will no longer be visible via the child class. More on reddit.com
10
17
February 24, 2024oop - Overriding class variables in python - Stack Overflow
I'm trying to understand a bit how Python (2.6) deals with class, instances and so on, and at a certain point, I tried this code: #/usr/bin/python2.6 class Base(object): default = "default va... More on stackoverflow.com
Thedigitalcatonline
thedigitalcatonline.com › blog › 2014 › 05 › 19 › method-overriding-in-python
The Digital Cat - Method overriding in Python
Method overriding is thus a strict part of the inheritance mechanism. As for most OOP languages, in Python inheritance works through implicit delegation: when the object cannot satisfy a request, it first tries to forward the request to its ancestors, following the specific language rules in the case of multiple inheritance. ... class Parent(object): def __init__(self): self.value = 5 def get_value(self): return self.value class Child(Parent): pass
W3Schools
w3schools.com › python › python_inheritance.asp
Python Inheritance
If you add a method in the child ... parent class, the inheritance of the parent method will be overridden. ... If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: sales@w3schools.com · If you want to report an error, or if you want to make a suggestion, send us an e-mail: help@w3schools.com · HTML Tutorial CSS Tutorial JavaScript Tutorial How To Tutorial SQL Tutorial Python Tutorial W3.CSS ...
DigitalOcean
digitalocean.com › community › tutorials › understanding-class-inheritance-in-python-3
Understanding Class Inheritance in Python 3 | DigitalOcean
August 20, 2021 - Since trout are typically freshwater fish, let’s add a water variable to the __init__() method and set it equal to the string "freshwater", but then maintain the rest of the parent class’s variables and parameters: ... ... class Trout(Fish): def __init__(self, water = "freshwater"): self.water = water super().__init__(self) ... We have overridden the __init__() method in the Trout child class, providing a different implementation of the __init__() that is already defined by its parent class Fish.
GeeksforGeeks
geeksforgeeks.org › python › method-overriding-in-python
Method Overriding in Python - GeeksforGeeks
July 12, 2025 - Example: Let's consider an example where we want to override only one method of one of its parent classes. ... # Python program to demonstrate # Python program to demonstrate # overriding in multilevel inheritance class Parent(): # Parent's show method def display(self): print("Inside Parent") # Inherited or Sub class (Note Parent in bracket) class Child(Parent): # Child's show method def show(self): print("Inside Child") # Inherited or Sub class (Note Child in bracket) class GrandChild(Child): # Child's show method def show(self): print("Inside GrandChild") # Driver code g = GrandChild() g.show() g.display()
Medium
medium.com › @officialyrohanrokade › demystifying-python-inheritance-parent-child-classes-method-overriding-and-the-power-of-super-8140fb2d8982
Python Inheritance Simplified: Parent-Child, Method Override & super() | by Rohan Rokade | Medium
May 8, 2025 - Method overriding allows a subclass to provide a specific implementation of a method that is already provided by its superclass. The method in the subclass should have the same name, signature, and parameters as the method in the superclass. ...
CodingNomads
codingnomads.com › python-subclass-method-override
Python Subclass: Method Override
Overriding parent methods is done by re-defining a new method or attribute with the same name inside the child class · The redefinition of the parent method automatically overrides the method · Method overriding offers additional customization ...
Manifoldapp
cuny.manifoldapp.org › read › how-to-code-in-python-3 › section › 79b92910-62a3-49eb-bef5-635ba534e692
Understanding Inheritance | How To Code in Python 3 | Manifold @CUNY
Since trout are typically freshwater fish, let’s add a water variable to the __init__() method and set it equal to the string "freshwater", but then maintain the rest of the parent class’s variables and parameters: ... ... class Trout(Fish): def __init__(self, water = "freshwater"): self.water = water super().__init__(self) ... We have overridden the __init__() method in the Trout child class, providing a different implementation of the __init__() that is already defined by its parent class Fish.
Python Tutorial
pythontutorial.net › home › python oop › python overriding method
Python Overriding Methods
March 31, 2025 - The overriding method allows a child class to provide a specific implementation of a method that is already provided by one of its parent classes. Let’s take an example to understand the overriding method better. ... class Employee: def __init__(self, name, base_pay): self.name = name ...
Medium
medium.com › @gauravverma.career › method-overriding-in-python-31ae477e7730
Method overriding in Python. Method overriding in Python occurs when… | by Gaurav Verma | Medium
September 8, 2024 - class Vehicle: def __init__(self, vehicle): print(vehicle, 'is a type of Vehicle.') def move(self, minspeed): print("Minimum speed of a vehicle should be ", minspeed, "km/hr") class Car(Vehicle): def __init__(self, cartype): print(cartype, 'is a Car') super().__init__(cartype) def move(self, minspeed): ''' Overriding move() method with matching signature :param minspeed: :return: ''' print("Minimum speed of a car should be ", minspeed, "km/hr") ###This method has different number of parameters ### from move() method present in parent (Vehicle) class ### This will result in error: ###Error: Signature of method 'Car.move()' does not match signature of the base method in class…
GitHub
github.com › python › mypy › issues › 15616
Cannot override class variable -- using `Final` and `ClassVar` · Issue #15616 · python/mypy
July 6, 2023 - But in practice, Mypy displays a type error when you use Final on a subclass where the parent class used a ClassVar. To Reproduce · from typing import ClassVar, Final, ClassVar, Literal class Animal: description: ClassVar[str] = "hard to generalize" class Dog(Animal): description: Final[str] = "very good" https://mypy-play.net/?mypy=latest&python=3.11&gist=69298f23e25b94da7dadc694769db16d · Expected Behavior · No error. Actual Behavior · Cannot override class variable (previously declared on base class "Animal") with instance variable [misc] You may be tempted to work around this with: class Dog(Animal): description: Final[ClassVar[str]] = "very good" But then Mypy outputs: Variable should not be annotated with both ClassVar and Final [misc] Your Environment ·
Author christianbundy
Tutorialspoint
tutorialspoint.com › python › python_method_overriding.htm
Python - Method Overriding
Additionally, the child class has one more instance variable incentive. We shall use built-in function super() that returns reference of the parent class and call the parent constructor within the child constructor __init__() method. class SalesOfficer(Employee): def __init__(self,nm, sal, inc): super().__init__(nm,sal) self.incnt=inc def getSalary(self): return self.salary+self.incnt · The getSalary() method is overridden to add the incentive to salary.
Reddit
reddit.com › r/learnpython › changing parent attributes through child class
r/learnpython on Reddit: Changing Parent attributes through child class
February 10, 2023 -
How can I change the attributes of my parent class trough the child class?
class Parent:
def __init__(self):
self.name = "this the parent"
class Child(Parent):
def __init__(self):
pass
def change_name(self):
Parent.name = "text changed"
thank you in advance
Top answer 1 of 3
2
I think i know what you want to do. I think you are trying to make a tree of objects where child objects can influence their parent objects. To do this you have to pass an instance of the parent into the child. Its easiest to do when creating it. class std_node(): def __init__(self,name,parent=None): self.name = name self.parent = parent # instantiate a parent p = std_node("parent") # instantiate a child c = std_node("child",p) # change parent name via child c.parent.name = "grand parent"
2 of 3
1
name is not a class attribute, hence you can't change it by doing Parent.name. It's an instance attribute and therefore referenced with self.name. class A: def __init__(self): self.name = "A" def get_name(self): return self.name class B(A): def __init__(self): super().__init__() A.name = "changed A" self.name = "B" a = A() b = B() print(a.name, b.name, A.name, B.name, sep=", ") This prints: A, B, changed A, changed A
Reddit
reddit.com › r/learnpython › confused about class variables, also with inheritance
r/learnpython on Reddit: Confused about class variables, also with inheritance
February 24, 2024 -
I'm finding class variables super confusing. I thought they were just like static variables in C++ (which instances can't own), but it seems they have quite different behavior.
Basic Class variable behavior - is this correct?
class Foo: x: int
-
if you set
Foo.x, it overrides the value of.xfor all instances of Foo, but -
if you set
.xon an instance ofFoo, it only changes.xon that instance.
edit: actually this can't be the full story, because sometimes changing Foo.x doesn't change the instance's .x??
Class variables + inheritance, what is going on?
class Parent: x: int class Child(Parent): pass Parent.x = 1 print(Child.x) # = 1. ok so child inherits parent class variable Child.x = 2 print(Parent.x) # = 1. ok, so child cannot set parent class variable Parent.x = 3 print(Child.x) # = 2. hol' up, now child doesn't inherit from parent anymore?
Also, if multiple classes inherit from Parent, if I set Child1.x does it affect the other children? How are instances affected too?
Class variables without declaration works too...?
What's the point of defining these variables in the class body if you don't need to?
class Foo: pass Foo.x = 3
I feel like there's some kind of mental model for class variables I'm just not understanding. Is there any easy way to think about them? Also is there any other weird behavior I should know?
Top answer 1 of 5
5
The class variables and instance variables remain separate if an instance variable of the same name is created. One doesn't override the other, but the class variable will no longer be readable via the object: In [1]: class c: ...: a = 1 ...: def __init__(self): ...: self.a = 2 ...: In [2]: obj = c() In [3]: c.a Out[3]: 1 In [4]: obj.a Out[4]: 2 As for inheritance, yes if you assign a value to a class variable on a child that has the same name as one of the parent's class variables, then a separate class variable of that name will be created for the child. Again, the two will remain separate, one readable from the parent and one readable from the child, but the parent's variable will no longer be visible via the child class.
2 of 5
4
If you do an attribute lookup on an instance and the attribute isn't found on the instance itself, it will look on the class next. If you do an attribute lookup on a class and it isn't found on the class itself, it will look on the parent class next. If you do an attribute assignment, however, that always sets the attribute directly on the thing itself. That means, if you do an attribute assignment on an instance, even if its class already has an attribute of that name, you create a new instance attribute rather than reassigning the class attribute. Importantly, a lookup of that attribute on the instance would now no longer propagate up to the class. The same is true for classes and their parent classes. This becomes clearer if you take a look at the special __dict__ attribute of your classes and objects as you do the assignments, which holds all direct attributes of the object or class in dictionary form.
Top answer 1 of 2
13
def showDefaultValue(cls, defl=default):
means that default gets evaluated when the function is defined, as usual in Python. So the definition looks like this then:
def showDefaultValue(cls, defl="default value in base"):
This value of defl is stored as a default argument on the function object and used when you call the method without arguments. You can look at the defaults of a function like print Descend.showDefaultValue.im_self.default to validate this.
If you want to get the default from the current class then you have get it from there:
@classmethod
def showDefaultValue(cls, defl=None):
if defl is None:
defl = cls.default
print "defl == %s" % (defl)
2 of 2
12
The class variable is being overwritten. Try
@classmethod
def showDefaultValue(cls):
print "defl == %s" % (cls.default,)
The reason your way doesn't work has more to do with the way Python treats default arguments to functions than with class attributes. The default value for defl is evaluated at the time Python defines the binding for showDefaultValue and this is done exactly once. When you call your method the default value used is what was evaluated at the time of definition.
In your case, defl was bound to the value of the default variable as it was during the execution of the class body form of Base. Regardless of how you call showDefaultValue later on (i.e., whether via Base or via Descend) that value remains fixed in all subsequent invocations of showDefaultValue.
Codecademy
codecademy.com › docs › python › inheritance
Python | Inheritance | Codecademy
June 19, 2025 - ... The child class __init__() method must initialize all necessary attributes, including those that would normally be handled by the parent class. The super() function is a built-in Python function that ...
CodeQL
codeql.github.com › codeql-query-help › python › py-overwritten-inherited-attribute
Overwriting attribute in super-class or sub-class — CodeQL query help documentation
#Attribute set in both superclass and subclass class C(object): def __init__(self): self.var = 0 class D(C): def __init__(self): self.var = 1 # self.var will be overwritten C.__init__(self) class E(object): def __init__(self): self.var = 0 # self.var will be overwritten class F(E): def __init__(self): E.__init__(self) self.var = 1 #Fixed version -- Pass explicitly as a parameter class G(object): def __init__(self, var = 0): self.var = var class H(G): def __init__(self): G.__init__(self, 1)
Mimo
mimo.org › glossary › python › override-method
Python Override Method: Syntax, Usage, and Examples
When you override methods in subclasses, you can call those methods through a shared parent interface. That’s called polymorphism. It lets you write flexible code that works across multiple types of objects without knowing exactly which type you're dealing with. Here are some beginner-friendly examples that show how method overriding in Python works in practice. ... class Animal: def sound(self): print("Some generic sound") class Dog(Animal): def sound(self): print("Bark") a = Animal() a.sound() # Output: Some generic sound d = Dog() d.sound() # Output: Bark