This question already has answers here:
What are metaclasses in Python?
(25 answers)
Why use Abstract Base Classes in Python?
(6 answers)
Closed last month.
I read two articles about Metaclassing in python:
What is a metaclass in Python?
http://jakevdp.github.io/blog/2012/12/01/a-primer-on-python-metaclasses/
And I read about the ABC(abstract base classes) which is presented at:
https://docs.python.org/2/library/abc.html.
So I have to ask: What is the difference between a metaclass and abstract base classes (ABC)?
As I can understand I can use both to define class creation from metaclasses (metaclass).
For what purpose I would use an ABC or 'my own' metaclass?
Related
This question already has answers here:
Making functions non override-able
(6 answers)
Prevent function overriding in Python [duplicate]
(3 answers)
How to prevent a function from being overridden in Python [duplicate]
(4 answers)
Closed 3 years ago.
With python abstract classes, is there a way to require that a class instance does not override a particular method?
Using the #abstractmethod decorator on a method requires the child class to define the method. Skipping the #abstractmethod decorator allows the child to skip defining the method and "silently inherent" the abstract method. What I'd like is something like a #onlyabstractmethod to decorate a method that I want to ensure the child does not override.
This question already has answers here:
How does the #property decorator work in Python?
(15 answers)
How do Python properties work?
(4 answers)
Closed 4 years ago.
I can do
class Foo(object):
x = property(lambda _: 123)
f = Foo()
f.x
to get 123
However, if I try
p = property(lambda : 123)
p
I get
<property object at 0x108f2f3b8>
Now I understand that an member of a class instance is not the same thing as a regular variable but I'm not sure what exactly makes this behavior different.
Does the fact that you instantiate a class somehow do extra binding on property objects? Is it a special case or is it a behavior I can take advantage in other situations and extend? Related - are property objects useful outside of a class declaration? Or is it just for this specific case?
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
python class inherits object
In Python 2.7, what is the difference between:
class MyClass(Object):
and
class MyClass:
What does the Object do?
The Object in this case the base class of MyClass, meaning that it 'inherits' the methods and variables of Object unless overwritten. Inheriting from object, however, creates a 'new-style class' as opposed to an 'old-style class'. For more information, see jozzas' comment
See this tutorial for information about inheritance.
This question already has answers here:
Why do Python classes inherit object?
(6 answers)
Closed 5 years ago.
In python class declaration I can declare a class by few ways. What is a difference between following samples?
class MyClass:
def __init__(self)
pass
class MyClass(object):
def __init__(self)
pass
The second declaration creates a new-style class. A new-style class is derived from a built-in type, in this case an object. This was introduced in python 2.2 in an effort to unify classes and types. For backward compatibility old-style classes are still the default
Additional read: http://docs.python.org/release/2.2.3/whatsnew/sect-rellinks.html
The second way creates a "new-style" class. Documentation is admittedly a bit lacking, as mentioned in a couple places on the python website Python Guide 3.3, and here. There's also an essay describing their design by Python's creator (Guido van Rossum), but it's not strictly documentation.
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Python: Difference between class and instance attributes
class a:
m = 1
def __init__(self):
self.n = 2
According to the book I am reading, m is called class attributes and n is called data attributes, but what's the difference between them?
It seems that the operations of them is nearly same. The only difference I can tell is one is in the function __init__ and another isn't.
This is essentially a duplicate of this question which has an example of the difference.
Python: Difference between class and instance attributes