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This article introduces the relevant knowledge of "how to write Python decorator". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Writing a decorator is a completely different skill. So first of all, you need to understand the following:

Closure

How to use a function as a "first type" parameter

Variable parameter

Parameter unpacking

Even some details of how Python loads the source code

What are the most important benefits of writing decorators? In your daily development, what does the decorator make you do that is easy and powerful?

I. Analysis, logging and guidance

Especially in large software, we usually need to specifically test what happened and record indicators that quantify different behaviors.

By encapsulating these important events in functions or methods within the decorator, the decorator can easily and easily handle the requirements just mentioned. For example: what way can be used to count or other indicators.

Second, verification and operation inspection

Python's type system is quite typed, but it is also very dynamic. All of these benefits also mean that some bug can be quietly generated, and these bug can be captured by more typed languages such as Java at compile time.

Even in the longer term, you may need to strengthen something more complex and be able to personalize the check as the data goes in and out. The decorator makes it easy for you to deal with all of this and can apply it to many functions at once.

Suppose: you have a bunch of functions, each of which returns a dictionary that contains a field called "summary".

The value of this field cannot exceed 80 characters in length; if it is violated, it is incorrect. Here is a decorator that can throw a value error (ValueError) when the condition is not met, as follows:

Third, create a framework

Once you have mastered the programming of the decorator, you will be able to benefit from the simple syntax of using the decorator, which allows you to add semantics to your code to make it easy to use. This is the next best tool to extend Python's own syntax.

In fact, many popular open source frameworks use decorators. The web application framework Flask uses decorators to route URLs to functions that handle HTTPS requests.

Here, you have a global object called app, which has a method called route (routing) and accepts specific parameters. This routing method returns a decorator that is applied to the handler.

Some complicated things happen under this mask, but from the point of view of Flask users, all these complexities are completely hidden.

The use of decorators in this way is also reflected in stock Python. For example, full use of the object system depends on the @ classmethod and @ property decorators:

This class has three different definition declarations. However, their meanings are different.

1:constructor is a normal method.

2:for_winter is a class method and provides something similar to a "workshop"

3:progess is read-only, dynamic property

For everyday purposes, the @ classmethod and @ property decorators are so simple that you can easily extend the object semantics of Python.

Improve your career

Writing decorators is not easy at first. It's not like rocket science, but it takes a lot of effort to learn and rule out nuances. And learning decorators does give you an advantage.

When you are the one on your team who knows and can write decorators, and the decorators you write can solve some practical problems, other developers will use your decorators.

Because, once the difficult parts of these decorators are done, the decorators will be easy to use. This has a great positive effect on the code you write. It will also make you an important role.

This is the end of "how to write Python decorator". Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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