[PYTHON] Personal best practice template to use when you want to make MVP with Flask

When creating a web application, it is convenient to have a template. This time, I would like to introduce the template of the Flask app that I usually use.

Premise

• OS: Windows 10
• Editor: Visual Studio Code
• Host on Heroku
• Python 3.6
• Flask 1.1.2
• gunicorn 20.0.4
• Created an environment with Anaconda.
• However, only gunicorn was not found in the Anaconda repository, so I installed it with pip.

Site overview

• TOP screen
• PRJ resource creation / reference / search function
• Facebook authentication function

It is a web application that creates and manages a simple PRJ with.

The main specifications of the site are as follows.

• Logged in person can create PRJ
• Site users can participate in PRJ from PRJ details
• Only PRJ members can update the progress of PRJ
• Only the PRJ creator (leader) can complete the PRJ

Folder structure

As mentioned above, it is a simple application, so it is a scale that can be written in one file, but I want to organize my folders neatly for extensibility and readability.

In particular, the folders were organized with the following points in mind.

• Separate folders according to processing hierarchy
• Separate files for each resource such as TOP / PRJ

The actual folder structure is as follows.

tree

root root folder
│  .gitignore         
│  LICENSE
│  main.py First application server body to be executed
│ Procfile Used when running on Heroku
│  README.md
│  requirements.txt Used when running on Heroku
│
├─.vscode VSCode configuration file (for gitignore)
│      launch.Define json debug configuration
│      settings.json Python virtual environment specification etc.
│
├─biz Business logic storage
│     prj.Write business logic such as py DB operations and API calls
│
├─mw middleware (filter) storage
│     prj.Write the overall processing of the middle layer that connects py route and biz
│
├─route Routing definition (blueprint) storage
│     prj.Write routing definitions for each py resource
│     top.Write routing definitions for each py resource
│
├─static Static content storage
│ ├─common Static content used on all pages
│  │  ├─css
│  │  │      page.css
│  │  │
│  │  └─js
│  │         page.js
│  │
│ ├─prj Static content storage by resource
│  │  ├─css
│  │  │      page.css
│  │  │
│  │  └─js
│  │          page.js
│  │
│ └─top Static content storage by resource
│      ├─css
│      │      page.css
│      │
│      └─js
│              page.js
│
└─ templates Jinja Template storage
   │  footer.html common footer
   │  header.html common header
   │  layout.html page layout definition
   │  top.Individual page for each html resource (1 file complete system)
   │
└─prj Individual page by resource (multi-page system)
           entry.html
           search.html
           show.html

Outline of processing

Start Flask server

When you start the Flask server, run main.py.

Online processing (display of TOP screen)

When the Flask server accepts a request from a user to the TOP page, it processes according to the following flow. There is no particular logic in the processing when the TOP page is displayed, and the corresponding template is simply returned, so the processing flow is as follows.

• User accesses https://my-site.com/ with a browser
• Flask server (main.py) receives the request and routes it to route / top.py
• route / top.py returns therender_template ('top')method
• Since the render_template ('top') method was returned, use template / top.html to configure the TOP page and return the result to the browser.

Online processing (display of PRJ screen)

The processing flow of the PRJ screen is roughly explained using the PRJ detailed screen as an example.

Unlike the TOP screen, the PRJ screen needs to implement multiple actions such as registration, search, and reference. Therefore, each layer has the following roles.

• route: Extracts actions from received requests and distributes processing (routing)
• mw: Define check process and biz process to call for each action
• biz: Access API and DB

By designing in this way, the process can be divided into each layer and managed in an easy-to-understand manner. It also makes it easier to see where to make corrections when adding new features.

※たとえば、新しいアクションdeleteを追加したければ、route、mw、biz、templateの各prj.py/prj.htmlにdeleteアクションに対応するメソッドを追加する、など。

• As another example, when acquiring prj information, if you want to acquire the user information of the prj creator from another entity, the user entity, you can handle it by adding the user acquisition process to mw / prj.py. Something.

As for the processing relationship between layers, we will implement it with the following policy.

• Each method in the route layer is defined in the unit of routing
• Each method of the route layer processes by combining the method call processing of the mw layer as you like.
• Each method of the mw layer is defined in any unit.
• Each method of the mw layer processes by combining the method call processing of the biz layer as you like.
• Each method in the biz layer performs one specific API call process or one DB access process.

Implementation details

maiy.py: Flask server startup process

Import * .py in the route folder and ʻApp.register_blueprint ()` so that various requests can be routed properly.

main.py

from flask import Flask, redirect, url_for

app = Flask(__name__)

from route.top import top
from route.prj import prj

app.register_blueprint(top)
app.register_blueprint(prj)

if __name__ == '__main__':
  app.debug = True
  app.run(host='127.0.0.1',port=5000)

route/top.py Only the process to display the TOP screen. Because it is the routing when the site route (https://my-site.com/) is accessed Blueprint's url_prefix sets '' (empty string).

route/top.py

from flask import Flask, render_template, request, Blueprint

top = Blueprint('top', __name__, url_prefix='')

@top.route('/')
def index():
  return render_template('top.html', title='TOP')

route/prj.py prj routing definition. Set the Blueprint url_prefix to '/ prj'. By doing this, you will be able to accept requests for https://my-site.com/prj/~. By defining the routing like @ prj.route ('/ search', methods = ['POST']), various actions such as https://my-site.com/prj/search are accepted. Will be able to be.

route/prj.py

from flask import Flask, render_template, request, Blueprint

from mw.prj import parse, search_prj, get_prj, create_prj, update_prj

prj = Blueprint('prj', __name__, url_prefix='/prj')

@prj.route('/')
def index():
  return render_template('prj/search.html', title='Project search', prj={})

@prj.route('/search', methods=['POST'])
def search():
  q = parse(request)
  if q is None:
    #Early return
    return jsonify({'code': 'W00100','message': 'The value entered is invalid.'})
  
  #Search DB based on the entered conditions
  data = search_prj(q)

  #Display search results
  return jsonify({'data': data})

@prj.route('/show/<prj_id>', methods=['GET'])
def show(prj_id):
  if prj_id is None:
    #Early return
    return render_template('prj/show.html', title='Project details', data={})
  
  # prj_Search DB by id
  data = get_prj(prj_id)

  #View details page
  return render_template('prj/show.html', title='Project details', data=data)

@prj.route('/entry', methods=['GET'])
def entry():
  #Initial display of PRJ input screen
  return render_template('prj/entry.html', title='Project creation')

@prj.route('/create', methods=['POST'])
def create():
  #Create PRJ
  data = create_prj(parse(request))
  #View details page
  return render_template('prj/show.html', title='Project details', data=data, message='I have created a project.')

mw/prj.py Write a check process and Biz call process to process each action.

mw/prj.py

from flask import request
import biz.prj as prj

def parse(request):
  #Omitted

def search_prj(dto):
  #Omitted

def get_prj(prj_id):
  """
Get the project with the specified project ID
  """
  return prj.get(prj_id)

def create_prj(dto):
  #Omitted

def update_prj(data, dto):
  #Omitted

biz/prj.py Write API access process and DB access process. The sample below describes a get process that calls the API over HTTP. Also, since API endpoints and API keys are confidential information as a system, they are set to be read from environment variables.

biz/prj.py

import requests
import os

api_endpoint = os.environ.get('API_ENDPOINT')
headers = {
  'x-api-key':os.environ.get('API_KEY')
}

def get(prj_id):
  r_get = requests.get(api_endpoint + '/prj/' + prj_id, headers=headers)
  return r_get.json()

template/layout.html Template for all HTML pages. CSS and JS common to all pages can be read and defined in this layout.html. I try not to write it on each page.

{% Block css%} and {% block js%} are defined so that CSS and JS individually for each page can be read.

The contents of the body tag are defined to be a common header, content of each page, and a common footer.

<link rel="stylesheet" href="/static/common/css/page.css" /> <script src="/static/common/js/page.js"></script> When reading static content under static, href and src are defined with a slash start like / static. This is the same layout.html for common static content under static / common / even if the page hierarchy is different like template / top.html and template / prj / show.html. This is so that it can be read using.

template/layout.html

<!DOCTYPE html>
<html>
<head>
<title>{{ title }}</title>
<meta http-equiv="Content-Type" content="text/html" charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1.0" />
<!--Common style-->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bulma/0.8.2/css/bulma.min.css">
<script defer src="https://use.fontawesome.com/releases/v5.3.1/js/all.js"></script>
<link rel="stylesheet" href="/static/common/css/page.css" />
<!--Individual page css-->
{% block css %}
{% endblock %}
</head>
<body class="has-navbar-fixed-top">

  <!--header-->
  {% include "header.html" %}

  <!--content-->
  {% block content %}
  {% endblock %}

  <!--footer-->
  {% include "footer.html" %}

  <!--Common JS-->
  <script src="https://code.jquery.com/jquery-2.1.1.min.js"></script>
  <script src="/static/common/js/page.js"></script>

  <!--Individual page JS-->
  {% block js %}
  {% endblock %}
</body>
</html>

template/top.html

template/top.html

{% extends "layout.html" %}
{% block css %}
<link rel="stylesheet" href="/static/top/css/page.css" type="text/css" />
{% endblock %}

{% block content %}
<section class="hero is-medium is-primary is-bold">
  <div class="hero-body">
    <div class="container">
      <div class="columns is-centered">
        <div class="column is-narrow">
          <h1 class="title is-1">
            Site Concept
          </h1>
        </div>
      </div>
    </div>
  </div>
</section>
{% endblock %}

{% block js %}
<script async src="/static/top/js/page.js"></script>
{% endblock %}

template/prj/show.html

template/prj/show.html

{% extends "layout.html" %}
{% block css %}
<link rel="stylesheet" href="/static/prj/css/page.css" type="text/css" />
{% endblock %}

{% block content %}
<section class="hero is-medium is-primary is-bold">
  <div class="hero-body">
    <div class="container">
      <div class="columns is-centered">
        <div class="column is-narrow">
          <h1 class="title is-1">
            {{ data['name'] }}
          </h1>
        </div>
      </div>
    </div>
  </div>
</section>
{% endblock %}

{% block js %}
<script async src="/static/prj/js/page.js"></script>
{% endblock %}

Full code for sample app

The application code being created using this template is published on Github. https://github.com/KeitaShiratori/ripple