Flask project learning (I) -- sayhello

Studying recently flask frame , On the one hand, the fastest way to learn is to read official documents . After reading the example project given by the official document , I also want to see some beginner projects to get familiar with this framework . therefore , As long as this series of blogs is to record their own learning flask The project source code viewed by the framework .

This article is mainly about sayHello project

1. Project brief introduction

project github The address is

https://github.com/greyli/sayhello

The project mainly consists of the following documents

according to README.md Explanation in , After installing the relevant environment dependencies , Start the project by

$ flask forge
$ flask run
* Running on http://127.0.0.1:5000/

After opening the page with a browser , This is the effect ：

The functional logic of this project is relatively simple , It's mainly about sending messages , Then everyone can see .

2. Process explanation

We can read the relevant code step by step according to the steps just performed .

2.1 forge Method

First, before starting , We executed an order

flask forge

This command literally means , Give Way flask Framework to implement a called forge Methods , From the source code , We can search whether there is this forge Keyword code ：

stay commands.py In file , There is indeed a man named forge Methods . By reading the notes , You can know that the main function of this method is to virtualize some information . And there's a count Parameters , It means how many messages should be virtual . For specific implementation , Is through a call Faker The object of , Afterlife output data , And then according to count Value to generate specific information ：

    for i in range(count):
        message = Message(
            name=fake.name(),
            body=fake.sentence(),
            timestamp=fake.date_time_this_year()
        )

2.2 index Method

In our web page input corresponding IP:PORT after , Will jump to the home page . therefore , We can see how the code of the home page is implemented . stay view.py in , You can find that the route is ’/' Corresponding method ：

This method includes two functions: front-end information submission and information display .
The first is to judge whether there is compliance submission , If there is a compliance submission , Just write the data into the database and reload the home page . For data submission , After getting the data from the front end , Will execute a name called flash Methods , This method mainly returns a prompt message to the front-end user . This message is displayed when rendering the template , Through get_flashed_messages() Method to get and render ：

Before loading the home page , Will message After sorting the data , Pass in to the template to fill , And back to the front end ：

    messages = Message.query.order_by(Message.timestamp.desc()).all()
    return render_template('index.html', form=form, messages=messages)

3. Entrance explanation

In this project , The entrance is __init__.py file

The first is to define this app The name is sayhello, And from settings.py The configuration file is loaded in . Then initialize the database according to the data of the loaded configuration file ,bootstrap etc. .
Finally, I will views, errors, commands Are loaded into the program .

Next , We can first look at what is written in the configuration file

First, according to different platforms , The database prefix is different . Then there's the setup SECRET_KEY, And database related configuration .

4. Other explanations

Because the logic of this project is relatively simple , I have just said all the code that the main process runs in this project . But there are also some codes that are not in the mainstream , We can talk about it alone .

4.1 errors.py

errors There are mainly two callback methods defined in , In the presence of 404,500 When , Call these two methods separately .

We can try it 404 The callback . Enter... In the browser ip:port, And follow a path that is not declared in the back end , You can 404

4.2 forms.py

forms It mainly defines a structure , It is the structure that the front end sends submission information to the back end . This structure inherits FlaskForm, Therefore, the main function of this structure is to transmit data at the front and rear ends . It is mainly divided into three attributes ： full name , Content , Submit .

4.3 models.py

models There is mainly a Message class , This class is inherited from db.Model. Therefore, it can be guessed that this kind of main function is related to the storage database . Every record will become a Message object , And store it in a database

5. Harvest

Through this project , I mainly learned the following skills

5.1 flash

flash You can return some interactive information to the user . For example, when logging in to an account, whether it is successful or unsuccessful , You need to give users a prompt . adopt flash Data written , It can be used in the front-end template file get_flashed_messages() Method to get . We can do a verification .

stay view.py Write another interface

@app.route('/flash',methods=['GET','POST'])
def test():
    flash(' Test it flash')
    return render_template('test.html')

And then in templates Build a new one inside test.html

<head>text</head>
<body>
    {
   {get_flashed_messages()}}
</body>

such , This interface is written . And then by visiting localhost:5000/flash You can verify this ：

5.2 404,500 Wait for page callback

flash have access to @app.errorhandler( Status code ) To recall which method to call when encountering the corresponding status code , Such as 404,500 etc. .