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Understanding Decorators in Python
Author: Juanjo Conti
Juanjo is a Systems Engineer. He has been programming in
Python for 5 years now and he uses the language to work,
investigate and have fun.
Blog: http://juanjoconti.com.ar
Email: jjconti@gmail.com
Twitter: @jjconti
The beginning of everything
Everything in Python is an object
• Identity
• Type
• Value
In Python everything is an object. Integers, strings, lists, tuples and other weirder things:
modules are objects, the source code is an object. Everything is an object. EVERYTHING.
Each object has 3 features or attributes: identity, type and value.
A note about what’s next
Next article is not an article properly speaking, it is the relief of a talk that was
presented in oral form, not from an audio medium but from my memory! I hope the
reader will find it useful.
Objects
Let’s see some examples. Number ‘1’ is an object. Using the built-in id we can find its
identity. Its type is int and its value is obviously 1.
>>> a = 1
>>> id(a)
145217376
>>> a.__add__(2)
3
Because it’s an object, we can apply to it some of its methods. __add__ is the method
that is called when we use the + symbol.
Other objects:
Introduction
The topics I treated in the talk are the following ones:
• The beginning of everything
• What is a decorator
• Decorator functions
• Decorators with parameters
• Decorator classes
• Decorating classes
[1, 2, 3] # lists
5.2 # floats
"hello" # strings
Functions
If everything is an object, so are the functions.
def greeting():
print "hello"
We can obtain a function’s id using id, access its attributes or even make another name
refer to the same function object: