Creating a Decorator in Python 2 to Enhance Class Method Execution

Learn how to implement a `pre_execution` decorator in Python 2 that calls a specific function before executing a method of a class, allowing you to intercept its arguments.
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Enhancing Class Method Execution in Python 2 with Decorators

In the realm of Python programming, decorators play a pivotal role in enhancing the functionality of functions and methods. If you're working with a class in Python 2 and want to execute a specific function every time a method is called, you've come to the right place! This guide will walk you through creating a pre_execution decorator that executes a custom function before your method runs, allowing you to intercept its arguments.

The Challenge: Intercepting Method Calls

You have a class named A with a method m(x) that returns x + 1. However, you want to create a decorator that adds a new function f which executes every time m is called. The decorator must allow function f to interact with the arguments passed to m.

The Original Code Structure

Let’s take a look at the existing code structure before we work on our solution:

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The Solution: Implementing pre_execution Decorator

Step 1: Understanding the Decorator

The task requires modifying the pre_execution function. The new implementation will save a reference to the original method and define a new method that calls the specified function f before executing the original method. Here’s the corrected version of pre_execution decorator:

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Step 2: Implementing the Decorator

In this improved version, when f is decorated, it is passed as an argument to patch_klass, which allows us to create new_method. This new_method executes f and then calls the original old_method.

Key Components:

Saving the Original Method: old_method = getattr(klass, method) stores a reference to the original method that we want to enhance.

Creating a New Method: The nested new_method calls f, then executes old_method, ensuring that f runs before and independently of m.

Step 3: Testing the Implementation

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This output confirms that the decorator works as intended; f runs before m and intercepts its arguments each time.

Conclusion: Mastering Decorators in Python 2

In this post, we explored how to create a pre_execution decorator in Python 2 to enhance method execution of a class. By modifying the decorator, we ensured that it executed our custom logic before calling the class method. This approach not only improves code reusability but also allows for cleaner and more maintainable code.

Harness the power of decorators, and you'll significantly enhance your Python programming skills!