Python Decorators Summary

Python decorators are a powerful feature that enables programmers to enhance or modify the behavior of a function without changing its code. A decorator is essentially a function that takes another function as an argument and returns a new function, which is often used for behavior modification, adding extra functionality, or performing preprocessing tasks.

1. Simple Decorator Example

A basic example of a decorator is my_decorator, which takes a function and returns a new function wrapper. The wrapper function adds behavior before and after the call to the original say_hello function.

2. Decorators with Parameters

Decorators can accept parameters for greater flexibility. In the example provided, repeat is a decorator factory that takes num_times as an argument to specify how many times the target function should be executed. The actual decorator is decorator_repeat, which returns the wrapper function.

3. Class Decorators

Python also supports class decorators, which work by implementing the __call__ method. DecoratorClass in the example is a class decorator that takes the target function and uses the __call__ method to mimic decorator functionality.

Application Examples

1. Logging Decorator

A common use case is logging, where a decorator log_time is used to record the execution time and other details of a function call.

2. Permission Check Decorator

In web applications, a decorator check_permission might be used to ensure that a user has the right to execute a function, raising a PermissionError if not.

3. Performance Optimization Decorator

For performance optimization, decorators like the built-in lru_cache can be used to cache function results to improve efficiency.