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Is it possible to decorator a function conditionally. For example, I want to decorate the function foo() with a timer function (timeit) only doing_performance_analysis is True (see the psuedo-code below).
if doing_performance_analysis: @timeit def foo(): """ do something, timeit function will return the time it takes """ time.sleep(2) else: def foo(): time.sleep(2) 
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To create a decorator function in Python, I create an outer function that takes a function as an argument. There is also an inner function that wraps around the decorated function. To use a decorator ,you attach it to a function like you see in the code below.
A decorator is a design pattern in Python that allows a user to add new functionality to an existing object without modifying its structure. Decorators are usually called before the definition of a function you want to decorate.
A decorator in Python is a function that takes another function as its argument, and returns yet another function . Decorators can be extremely useful as they allow the extension of an existing function, without any modification to the original function source code.
Decorators use a special syntax in JavaScript, whereby they are prefixed with an @ symbol and placed immediately before the code being decorated.
Decorators are simply callables that return a replacement, optionally the same function, a wrapper, or something completely different. As such, you could create a conditional decorator:
def conditional_decorator(dec, condition): def decorator(func): if not condition: # Return the function unchanged, not decorated. return func return dec(func) return decorator Now you can use it like this:
@conditional_decorator(timeit, doing_performance_analysis) def foo(): time.sleep(2) The decorator could also be a class:
class conditional_decorator(object): def __init__(self, dec, condition): self.decorator = dec self.condition = condition def __call__(self, func): if not self.condition: # Return the function unchanged, not decorated. return func return self.decorator(func) Here the __call__ method plays the same role as the returned decorator() nested function in the first example, and the closed-over dec and condition parameters here are stored as arguments on the instance until the decorator is applied.
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A decorator is simply a function applied to another function. You can apply it manually:
def foo(): # whatever time.sleep(2) if doing_performance_analysis: foo = timeit(foo) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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