Python 3.7.3 : Using the flask - part 010.

If you read my last tutorial about flask then you understand how to use the structure flask project with views.py and models.py.
If you run it and open the browser with http://127.0.0.1:5000/texts/ the result will be this:

{"texts":[{"title":"first title","txt_content":"this is first content"},{"title":null,"txt_content":null}]}

Let's create a file .env into the base folder named my_flask and add this source code:

SECRET_KEY='secret key'
DEBUG=True
SQLALCHEMY_TRACK_MODIFICATIONS = False
SQLALCHEMY_DATABASE_URI = sqlite:///texts.sqlite

Let's create a settings.py file into blue_test folder to get these settings:

import os
from os import environ
SECRET_KEY = os.environ.get('SECRET_KEY')
SQLALCHEMY_DATABASE_URI = os.environ.get('SQLALCHEMY_DATABASE_URI')

My blue_test project comes with the old views.py and a new routes.py file with this source code:

from flask import Blueprint, jsonify, request

api = Blueprint('api', __name__)

@api.route('/')
def home():
    return jsonify({'result' : 'You are in main page!'}) 

I create an extensions.py python script to deal with the database, see the source code:

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

With this new python file will solve the avoid circular importing of circular dependency of importing db.
This changes can be made on models.py and views.py, like this:

# import db from base folder, see dot
from .extensions import db 

This two files views.py and routes.py come with two Blueprint's: main and api.
Into the __init__.py will need to import and register both :

from .extensions import db
from .models import Texts
from .routes import api
from .views import main
...
    app.register_blueprint(main)
    app.register_blueprint(api)

If you run it into my_flask folder with:

C:\Python373\my_flask>set FLASK_APP=blue_test

C:\Python373\my_flask>flask run
 * Serving Flask app "blue_test"
 * Environment: production
...

The result into the browser area with http://127.0.0.1:5000/ for the routes.py blueprint api will be:

{"result":"You are in main page!"}

The result into the browser area with http://127.0.0.1:5000/texts/ for the views.py blueprint main will be:

{"texts":[{"title":"first title","txt_content":"this is first content"},{"title":null,"txt_content":null}]}

This shows you how to link multiple blueprints into one project.
You can see the full project at my GitHub project.

Python 3.7.3 : Using the flask - part 009.

In this tutorial, I will show you how to use blueprints with a new type of flask project using multiple python files.
I show you just how to create the A.P.I. not the REACT front end.
Flask uses a concept of blueprints for making application components and supporting common patterns within an application or across applications. Blueprints can greatly simplify how large applications work and provide a central means for Flask extensions to register operations on applications. A Blueprint object works similarly to a Flask application object, but it is not actually an application. Rather it is a blueprint of how to construct or extend an application., see the official webpage.
In my my_flask folder, I create a blue_test folder with three python files: __init__.py, views.py, and models.py.
The __init__.py file has this source code:

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

# create path for SQLAlchemy
import os
basedir = os.path.abspath(os.path.dirname(__file__))

db = SQLAlchemy()

def create_app():
    app = Flask(__name__)
    # instantiate config for SQLAlchemy
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
    app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(basedir, 'texts.sqlite')
    # init db 
    db.init_app(app)
    # avoid circular importing of circular dependency 
    from .views import main
    app.register_blueprint(main)
    return app

The views.py come with this source code:

from flask import Blueprint
from flask import jsonify, request
from . import db
from .models import Texts

main = Blueprint('main', __name__)
@main.route('/add_text', methods = ['POST'])
def add_text():
    txt_data = request.get_json()
    new_txt = Texts(title=txt_data['title'], txt_content=txt_data['txt_content'])
    db.session(new_txt)
    db.session.commit()
    # 201 status code for create successfully
    return 'Done', 201
@main.route('/texts/')
def texts():
    txt_list=Texts.query.all()
    texts=[]
    for txt in txt_list:
        texts.append({'title': txt.title, 'txt_content':txt.txt_content})
    return jsonify ({'texts':texts})

The models.py has this source code:

# import db from base folder, see dot
from . import db 

class Texts(db.Model):
    # primary key 
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(50))
    txt_content = db.Column(db.String(1000))

Use the base folder of the blue_test folder to instantiate the database named texts.sqlite with a table texts.

C:\Python373>cd my_flask

C:\Python373\my_flask>python
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD6
4)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from blue_test.models import Texts
>>> from blue_test import db, create_app
>>> db.create_all(app=create_app())
>>> exit()

If not run into the base folder then you get this error:

    from . import db
ImportError: attempted relative import with no known parent package

Now you will have a texts.sqlite file for the database.
Use this command to set FLASK_APP:

C:\Python373\my_flask>set FLASK_APP=blue_test
C:\Python373\my_flask>flask run

Now, using the postman you can test it by running the python script and call these methods.

Python 3.7.3 : Using the flask - part 008.

The tutorial for today will show you how to understand the flash method and fix exceptions.
First, the Flask module contains a flash method which passes a message to the next request, which generally is a template.
This lets you create feedback to users of a web application is critical, from notifications and error messages to warnings and progress alerts.
This system allows us to record a message at any point within a request, then display it at the start of the next request (and only the next request), see the documentation.
You need to import the flash with:

from flask import flash

The flash function takes up to 2 arguments, a message and a category like this: flash("message", "category").
In the next example, the random range output named out will send a flash message by category.
The flash warning category will send the number get by the random and will be into a range of 1 and 3.
Flashed messages are stored in the session until they are read it.
The HTML5 page named home.html can be found at my GitHub project.
This source code will send one message by flash and show two messages into a webpage.

@app.route('/',methods = ['GET','POST'])
def home():
    # test flash message
    out = random.randint(1,10)
    if out in range(1,3):
        flash(str(out),"warning" )
    if out in range(4,6):
        flash("This is a flash test for home.html with result:","success")
    if out in range(7,10):
        flash("This is a flash test for home.html with result:","danger")  
    return render_template("home.html")

The next example shows you how to use flash and exceptions to create an output error with render_template_string.
The output exception sends by flash without an HTML5 page request.

from flask import render_template_string
...
# fix Exception error , like 404
@app.errorhandler(Exception)
def page_not_found(e):
    flash(e, type(e))  
    return render_template_string('''
      {% with messages = get_flashed_messages(with_categories=true) %}
        {% if messages %}
          {% set printed_messages = dict() %}
          {% for category, message in messages %}
            {% if message not in printed_messages %}
              
{{message}}
{% set x = printed_messages.__setitem__(message, "value")  %}
            {% endif %}
          {% endfor %}
      {% endif %}
    {% endwith %}
    ''')

If you put a bad path URL intro the server ( http://127.0.0.1:5000/bad ) then you get the result of the exception 404:

404 Not Found: The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

Using the flash you can create your own notification system.

Python 3.7.3 : Using the flask - part 007.

This will be a long tutorial because will try to link some information's from the last tutorials.
First, the structure of the project can see into my GitHub project.
I create new templates and another python script named tserv.py for testing.
You can see easier how the POST method works and how to deal with a python database issue.
This script comes with an upload file feature and upload database with sqlite3 python module.
First, for upload a file we need the HTML5 file from templates folder named upload.html.
I update the base.html file to use the bootstrap framework.

import sqlite3
class UploadForm(FlaskForm):
    file = FileField()
    submit = SubmitField("submit")
    
@app.route('/upload',methods = ['GET','POST'])
def upload():
    form = UploadForm()
    
    if request.method == "POST" and form.validate():
        if form.validate_on_submit():
            file_name = form.file.data
            file_database(name = file_name.filename,data = file_name.read())
            print("File {}".format(file_name.filename))
            return render_template("upload.html", form = form)
    return render_template("upload.html", form = form)
def file_database(name,data):
    con=sqlite3.connect("file_upload.db")
    cursor = con.cursor()
    cursor.execute("""CREATE TABLE IF NOT EXISTS my_table (name TEXT, data BLOP) """)
    cursor.execute("""INSERT INTO my_table (name , data ) VALUES (?,?) """, (name, data))
    con.commit()
    cursor.close()
    con.close()

Let's run it:

python tserv.py

Into the main folder a database will be create and will fill with the file uploaded.
Now, if you want to add more we can create a download button into our UploadForm, is no need to have another python class.
First create your form tag into upload.html file and link with the python tserv.py code show bellow:

from flask import send_file
from io import BytesIO
...
@app.route('/download', methods=['GET','POST'])
def download():
    form = UploadForm()
    if request.method == "POST":
        con = sqlite3.connect("file_upload.db")
        cursor = con.cursor()
        cur_ex = cursor.execute(""" SELECT * FROM my_table """)
        for i in cur_ex.fetchall():
            name=i[0]
            data=i[1]
            break
        con.commit()
        cursor.close()
        con.close()
        return send_file(BytesIO(data), attachment_filename='test', as_attachment=True)
    return render_template("home.html", form = form)

When you run it the download button will download the first file upload into database.
This example tutorial can be more complex.
For example, you can show the database content into a new HTML file and then save with an open dialog to disk.

Python 3.7.3 : Using the flask - part 006.

Today I will show you how to use the RESTful API application with flask python module that uses HTTP requests to GET, PUT, POST and DELETE data.
When HTTP is used, as is most common, the operations (HTTP methods) available are GET, HEAD, POST, PUT, PATCH, DELETE, CONNECT, OPTIONS and TRACE.[2], see the Wikipedia article.
All of these HTTP methods will be tested with postman software.
You need to have an account and use the downloaded software in order to interrogate with these methods.
Let's see the source new code first:

@app.route("/users/", methods=['GET'])
def users():
    users = User.query.all()
    #return users_schema.jsonify(users)
    all_users = users_schema.dump(users)
    return jsonify(all_users.data)

@app.route("/users/", methods=['POST'])
def user_post(id):
    user_post = User.query.get(id)
    print(user_post)
    username = request.json['username']
    email = request.json['email']
    user_post.username = username
    user_post.email = email
    db.session.commit()
    return user_schema.jsonify(user_post)

@app.route("/users/", methods=['PUT'])
def user_put(id):
    user_put = User.query.get(id)
    print(user_put)
    username = request.json['username']
    email = request.json['email']
    user_put.username = username
    user_put.email = email
    db.session.commit()
    return user_schema.jsonify(user_put)

@app.route("/users/", methods=['DELETE'])
def user_delete(id):
    user_delete = User.query.get(id)
    print(user_delete)
    db.session.delete(user_delete)
    db.session.commit()
    return user_schema.jsonify(user_delete)

Using the postman you can test it by running the python script and call these methods at http://127.0.0.1:5000/users/.

Python 3.7.3 : Using the flask - part 005.

In the last tutorial, I used the flask-sqlalchemy python module.
Today I will show you how to use the flask_marshmallow python module.
First, let's take a look at this python module, see the official webpage:
Flask-Marshmallow is a thin integration layer for Flask (a Python web framework) and marshmallow (an object serialization/deserialization library) that adds additional features to marshmallow, including URL and Hyperlinks fields for HATEOAS-ready APIs. It also (optionally) integrates with Flask-SQLAlchemy.
The base class User will need to be integrated with this python module:

from flask import Flask
from flask import render_template
from forms import SignUpForm
from flask import request

from flask import jsonify
from flask_sqlalchemy import SQLAlchemy
from flask_marshmallow import Marshmallow
import os
from forms import AddUser

app = Flask (__name__)
app.config['SECRET_KEY'] = 'abcdefg'
# set SQLAlchemy
basedir = os.path.abspath(os.path.dirname(__file__))
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///' + os.path.join(basedir, 'server.sqlite')
db = SQLAlchemy(app)
ma = Marshmallow(app)
class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(80), unique=True)
    email = db.Column(db.String(120), unique=True)

    def __init__(self, username, email):
        self.username = username
        self.email = email
    '''
    def __rep_(self):
        return '' % self.username
    '''
class UserSchema(ma.ModelSchema):
    class Meta:
        model = User
user_schema = UserSchema()
users_schema = UserSchema(many=True)

@app.route("/users/", methods=['GET'])
def users():
    users = User.query.all()
    #return users_schema.jsonify(users)
    all_users = users_schema.dump(users)
    return jsonify(all_users.data)

# the default name main
if __name__ == '__main__':
    app.run(debug=True)

Let's take a look at http://127.0.0.1:5000/users/ and see the result:

[
  {
    "email": "catafest@yahoo.com", 
    "id": 1, 
    "username": "catafest"
  }, 
  {
    "email": "test@test.com", 
    "id": 2, 
    "username": "user_test"
  }
]