advanced python techniques: decorators

Advanced Python Techniques: Decorators

Tomo Popović

Žabljak 2015

Python Programming Language

● Extremely popular in recent years● Open Source● Great community● Supported by both the universities and industry

IT'15 Conference Žabljak, © 2015 Copyright T. Popovic

Decorators

● Easy to use● Can be used to implement loggers, timers,

format conversions, frameworks● Example of the use:


Objects in Python


Functions as objects

● Functions are first class objects:– They have types

– They can be elements of data structures (lists)

– They can appear in expressions● As part of an assignment statement● As arguments to a function


Closures

● A closure is a first class function● A closure can be stored as a variable● A closure has an ability to access other

variables local to the scope in which it was created


Decorators: Definition

● A decorator is typically a function that takes another function as an argument, referred to as decorated function, and then returns a new function.

● The returned function replaces or augments the behavior of the decorated function.


Implementation using classes


Implementation using functions


Decorators with Arguments


An example: execution timer


Conclusions

● A decorator is a callable object that accepts one argument, which is a reference to the function being decorated. It returns a reference to a function which augments the behavior of the decorated function.

● This paper illustrates implementing of decorators using Python classes or functions. Decorators with arguments are described as well.

● Multiple decorators can be applied to a single function.● Hopefully, the work will inspire further exploration of

decorators and other Python techniques.


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