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POWhat is the difference between Python decorators and the decorator pattern?
 

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  1. POWhat is the difference between Python decorators and the decorator pattern?
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    <p>What is the difference between “Python decorators” and the “decorator pattern”?</p> <p>When should I use Python decorators, and when should I use the decorator pattern?</p> <p>I'm looking for examples of Python decorators and the decorator pattern accomplishing same.</p> <p><strong>@AcceptedAnswer</strong></p> <p>I know that <a href="https://stackoverflow.com/a/8328867/708764">Jakob Bowyer's answer</a> is valid. Yet it's Strikar's answer that made me understand why.</p> <p>After Srikar's answer and studying given resources I've written this example, so I can visualize and understand Python decorators and the decorator pattern.</p> <p>I must <strong>disagree</strong> with Strikar's "<em>Python decorators are not an implementation of the decorator pattern</em>". After what I've learned <strong>I'm strongly convinced that Python decorators are implementation of the decorator pattern.</strong> Just not in the classic way.</p> <p><strong>Also</strong>, I need to add that despite the fact that Strikar said "<em>Python decorators add functionality to functions and methods at definition time</em>" <strong>you can easily use Python decorators at run time</strong>.</p> <p>Yet, I still mark Stiker's answer as accepted, because it helped me understand <a href="http://www.python.org/dev/peps/pep-0318/" rel="nofollow noreferrer"><strong>the implementation</strong></a> <strong>of the decorator pattern in Python</strong>.</p> <pre><code>""" Testing Python decorators against the decorator pattern """ def function(string): return string def decorator(wrapped): def wrap(string): # Assume that this is something useful return wrapped(string.upper()) return wrap def method_decorator(wrapped): def wrap(instance, string): # Assume that this is something useful return wrapped(instance, string.upper()) return wrap @decorator def decorated_function(string): print('! '.join(string.split(' '))) class Class(object): def __init__(self): pass def something_useful(self, string): return string class Decorator(object): def __init__(self, wrapped): self.wrapped = wrapped def something_useful(self, string): string = '! '.join(string.split(' ')) return self.wrapped().something_useful(string) @method_decorator def decorated_and_useful(self,string): return self.something_useful(string) if __name__ == '__main__': string = 'Lorem ipsum dolor sit amet.' print(function(string)) # Plain function print(decorator(function)(string)) # Python decorator at run time print(decorated_function(string)) # Python decorator at definition time a = Class() print(a.something_useful(string)) # Plain method b = Decorator(Class) print(b.something_useful(string)) # Decorator pattern print(b.decorated_and_useful(string)) # Python decorator decorated the decorator pattern </code></pre>
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    1. CO@Srikar is correct. [Here](http://stackoverflow.com/q/3118929/146792)'s another SO question that you might find interesting though!
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      1. USmac
    2. CO@Srikar, I can't accept Snswer that do not resolve problem descriped in Question, sorry, but most of proposed solutions in my questions are not working.
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    3. CO@seler fair enough.
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