Python What Is A Decorator : Lindakendall

Python What Is A Decorator

A decorator is a Python function that takes another function as its argument, and returns a new function. In other words, decorators allow you to modify the behavior of existing functions without modifying their source code. This can be useful for adding additional functionality to existing functions, such as logging, error handling, or caching.

Decorators are defined using the @ symbol followed by the name of the decorator function. For example, the following decorator prints the name of the decorated function before it is called:

```python def my_decorator(func): def wrapper(*args, **kwargs): print(f"Calling {func.__name__}") return func(*args, **kwargs) return wrapper @my_decorator def my_function(): print("Hello, world!") ```

When the my_function function is called, the my_decorator function is executed first. The my_decorator function then returns a new function (the wrapper function) which is assigned to the name my_function. When the wrapper function is called, it prints the name of the decorated function (my_function) before calling the original function.

Decorators can be used to add a wide variety of functionality to existing functions. Some common uses include:

Logging: Decorators can be used to log the input and output of a function, or to log any errors that occur during execution.
Error handling: Decorators can be used to handle errors that occur during the execution of a function. For example, a decorator can be used to automatically retry a function if it fails, or to send an email notification if an error occurs.
Caching: Decorators can be used to cache the results of a function call, so that subsequent calls to the function can be served from the cache. This can improve the performance of an application by reducing the number of times that a function needs to be executed.

Decorators are a powerful tool that can be used to extend the functionality of existing Python functions. They are easy to use and can be applied to any function, regardless of its complexity.

How to Create a Decorator

To create a decorator, you simply define a function that takes another function as its argument. The decorator function should return a new function that wraps the original function. The wrapper function can then add additional functionality to the original function, such as logging, error handling, or caching.

The following example shows how to create a decorator that logs the input and output of a function:

```python import functools def logging_decorator(func): @functools.wraps(func) def wrapper(*args, **kwargs): print(f"Calling {func.__name__} with args {args} and kwargs {kwargs}") result = func(*args, **kwargs) print(f"{func.__name__} returned {result}") return result return wrapper ```

To use the logging_decorator, simply apply it to the function that you want to log. For example:

```python @logging_decorator def my_function(): print("Hello, world!") ```

When the my_function function is called, the logging_decorator function will be executed first. The logging_decorator function will then return a new function (the wrapper function) which is assigned to the name my_function. When the wrapper function is called, it will print the name of the decorated function (my_function), the arguments passed to the function (args), and the keyword arguments passed to the function (kwargs). The wrapper function will then call the original function (my_function) and print the result of the function call.

Conclusion

Decorators are a powerful tool that can be used to extend the functionality of existing Python functions. They are easy to use and can be applied to any function, regardless of its complexity. If you are looking for a way to add additional functionality to your Python functions, decorators are a great option.