Decorator About
Decorator is an object, which takes another object as it's argument
Since Python 2.4: PEP 318 -- Decorators for Functions and Methods
Since Python 3.9: PEP 614 -- Relaxing Grammar Restrictions On Decorators
Decorator can do things before call
Decorator can do things after call
Decorator can modify arguments
Decorator can modify returned value
Decorator can avoid calling
Decorator can modify globals
Decorator can add or change metadata
Syntax
funcis a reference to function which is being decoratedargsarbitrary number of positional argumentskwargsarbitrary number of keyword argumentsBy calling
func(*args, **kwargs)you actually run original (wrapped) function with it's original arguments
Decoration
Decorator Types
Decorator function
Decorator method
Decorator class
Decorator Function
Decorator is a function which takes another object as an argument
Doesn't matter, whether this object is a function, class or method
Decorator Method
Decorator is a method which takes instance and another object as an argument
Doesn't matter, whether this object is a function, class or method
Decorator Class
Decorator is a class which takes another object as an argument to
__init__()methodDoesn't matter, whether this object is a function, class or method
Decorator Wrapper
Wrapper function
Wrapper lambda
Wrapper class
Wrapper method
Name
Name
wrapperis just a convention
Wrapper Function
objis a decorated objectDoesn't matter, whether is a function, class or method
Wrapper Lambda
objis a decorated objectDoesn't matter, whether is a function, class or method
Wrapper Class
If
objandWrapperare classes,Wrappercan inherit fromobj(to extend it)
Wrapper Arguments
If you know names of the arguments you can use it in wrapper
argsarbitrary number of positional argumentskwargsarbitrary number of keyword arguments
Decorator About Object
Decorating function
Decorating class
Decorating method
Decorating Function
By convention
funcorfn
Decorating Class
By convention
cls
Decorating Method
By convention
mth,methormethod
Decorator About Arguments
Without Arguments
With Positional Arguments
With Mixed Arguments
With Keyword Arguments
Without Arguments
With Positional Arguments
With Mixed Arguments
With Keyword Arguments
Decorate Function
Decorator must return reference to
wrapperwrapperis a closure functionwrappername is a convention, but you can name it anyhowwrappergets arguments passed tofunction
Decorate Stacked
Decorate Method
decorateis a decorator namemethodis a method nameselfis an instanceargsarbitrary number of positional argumentskwargsarbitrary number of keyword arguments
Syntax
decorateis a decorator namemymethodis a method nameselfis an instanceargsarbitrary number of positional argumentskwargsarbitrary number of keyword arguments
Decorate Class
decorateis a decorator nameMyClassis a class name
Syntax
decorateis a decorator nameMyClassis a class name
Decorator Function
funcis a reference to function which is being decoratedargsarbitrary number of positional argumentskwargsarbitrary number of keyword argumentsBy calling
func(*args, **kwargs)you actually run original (wrapped) function with it's original arguments
Decorator Method
MyClassis a class containing decoratordecorateis a decorator namemyfunctionis a function namefuncis a reference to function which is being decorated
Decorator Class
decorateis a decorator namemyfunctionis a function namefuncis a reference to function which is being decorated
Decorator Arguments
Used for passing extra configuration to decorators
Use more one level of nesting
Decorator Stdlib Functools
Wraps
from functools import wraps@wraps(func)
Cached Property
from functools import cached_property@cached_property(method)
LRU (least recently used) cache
from functools import lru_cache@lru_cache(maxsize=None)