1. Introduction<\/h2>\n
REST<\/strong> stands for Representational state transfer and it fits in the HTTP protocol designed worldwide for the users. RESTful is \u2013<\/p>\n To start with this tutorial we will need to install Python and set up some of the python libraries. Let us go ahead and install them one by one.<\/p>\n If someone needs to go through the Python installation on Windows, please watch this<\/a> link. You can download the Python from this<\/a> link.<\/p>\n Once the python is successfully installed on your system you can install the Flask-SQLAchdemy<\/strong> using a simple Installation command<\/em><\/span><\/p>\n Once you trigger this command the installation will be started as shown in Fig. 1.<\/p>\n Once the python is successfully installed on your system you can install the psycopg2<\/strong> using a simple Installation command<\/em><\/span><\/p>\n To start with the tutorial, I am hoping that you have the Postgres up and running in your local host environment. For easy setup, I have the database up and running on the docker environment. You can execute the below command to get the container running on docker in minutes.<\/p>\n Docker container run command<\/em><\/span><\/p>\n If everything goes well the container would be started successfully as shown in Fig. 2. You can use the Once the docker container is successfully started we need to create a database. Connect with the server on port 5433 using the pgAdmin<\/a> tool and create a new database named – Create database sql command<\/em><\/span><\/p>\n Before going any deeper in the practice I am assuming that you are aware of the Python and SQL basics. Let us dive in with the programming stuff now.<\/p>\n Add the following code to the python script containing the configuration wherein we will specify the database identifier containing the user, password, host, port, and database name information (In the ideal case this information will be fetched from some configuration file and not<\/em> directly hard coded here). This information will be used by the The python script contains the config.py<\/em><\/span><\/p>\n To build a simple web application and manipulate the data we need to map the database columns with the request model. With model.py<\/em><\/span><\/p>\n To automatically create the model structure we will need to run this file from the python console. Open the command prompt terminal and go to the project location. From the project, location write Db migrate commands<\/em><\/span><\/p>\n If everything goes well the table will be created and can be verified from the pgAdmin<\/a> console as shown in Fig. 3.<\/p>\n Now that we have the database and table connected with our flask application so let us implement the CRUD operations. In the below python script we will create the four HTTP operations i.e. POST, PUT, DELETE, and GET. The file consists of the \u2013<\/p>\n Let us write some API resource implementation i.e.<\/p>\n app.py<\/em><\/span><\/p>\n Run this python script and let us try adding a new book using a tool like Postman<\/a>.<\/p>\n Once the Application Endpoints<\/em><\/span><\/p>\n You can also download the postman collection from the Downloads<\/a> section. That is all for this tutorial and I hope the article served you with whatever you were looking for. Happy Learning and do not forget to share!<\/p>\n In this tutorial, we learned:<\/p>\n You can download the source code of this tutorial from the Downloads<\/a> section.<\/p>\n\n
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1.1 Setting up Python<\/h3>\n
1.2 Setting up Flask-SQLAchdemy<\/h3>\n
pip<\/code> command. You can fire the below command from the command prompt and it will successfully download the module from pypi.org<\/a> and install it.<\/p>\npip install -U Flask-SQLAchdemy\n<\/pre>\n
![\"Flask](\"https:\/\/examples.javacodegeeks.com\/wp-content\/uploads\/2021\/04\/pip-install-flask-sqlalchemy.jpg\")
<\/a>1.3 Setting up Psycopg2<\/h3>\n
pip<\/code> command. You can fire the below command from the command prompt and it will successfully download the module from pypi.org<\/a> and install it.<\/p>\npip install psycopg2\n<\/pre>\n
1.4 Setting up Postgres database<\/h3>\n
docker run -d -p 5433:5432 -e POSTGRES_PASSWORD=password --name postgres postgres\n<\/pre>\n
docker ps -a<\/code> command to confirm that the container is started successfully. For further information on docker basics, you can navigate to this tutorial<\/a>.<\/p>\n![\"Flask](\"https:\/\/examples.javacodegeeks.com\/wp-content\/uploads\/2021\/04\/docker-postgres-container-img1.jpg\")
<\/a>library<\/code>. To create a database you will use the following SQL command.CREATE DATABASE library\n<\/pre>\n
2. Create a Web App with Python Flask and PostgreSQL<\/h2>\n
2.1 Creating a Configuration<\/h3>\n
flask-sqlachemy<\/code> module to work with the database from the python application.<\/p>\n\n
postgres<\/code><\/li>\n5432<\/code><\/li>\ncreate_app()<\/code> method that returns the Flask app instance. You are free to change these details as per your configuration setup.<\/p>\nfrom flask import Flask\n\n\ndef create_app():\n app = Flask(__name__)\n app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False\n # sql config params\n app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql:\/\/postgres:password@localhost:5433\/library'\n return app\n<\/pre>\n
2.2 Creating a Database Model<\/h3>\n
libaray<\/code> database in place we will use the Flask-SQLAlchemy<\/code> extension in python to add the database layer capabilities. The file consists of the Flask-SQLAlchemy<\/code> instance called db<\/code> and will be used for database-related operations like create the table structure in the database and defining the data that we will store.<\/p>\nfrom flask_sqlalchemy import SQLAlchemy\n\nfrom config import create_app\n\ndb = SQLAlchemy(create_app())\n\n\n# model class to create table structure in db\nclass Book(db.Model):\n __tablename__ = 'books'\n\n id = db.Column(db.Integer, primary_key=True)\n title = db.Column(db.String(100), nullable=False)\n genre = db.Column(db.String())\n author = db.Column(db.String(), nullable=False)\n quantity = db.Column(db.Integer, nullable=False, default=0)\n\n def __init__(self, title, genre, author, quantity):\n self.title = title\n self.genre = genre\n self.author = author\n self.quantity = quantity\n\n def __repr__(self):\n return f'{self.id}'\n<\/pre>\npython<\/code> and click enter. Once you enter the python console trigger the following commands to automatically create the table schema<\/em> inside the library<\/code> table based on the model specified above.<\/p>\nfrom model import db\n\ndb.create_all()\n\nexit()\n<\/pre>\n
![\"Flask](\"https:\/\/examples.javacodegeeks.com\/wp-content\/uploads\/2021\/04\/book-table-pgadmin-img1.jpg\")
<\/a>2.3 Creating and Reading Entities<\/h3>\n
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app<\/code><\/li>\nFlask-SQLAlchemy<\/code> instance called db<\/code> and will be required for CRUD operations<\/li>\n<\/ul>\n\n
save_book()<\/code>: HTTP POST operation to save the new book in the table<\/li>\nget_books(\u2026)<\/code>: HTTP GET operation to get all the books from the table<\/li>\nhandle_book(book_id)<\/code>: HTTP GET\/PUT\/DELETE\/ operation on a book in the table<\/li>\n<\/ul>\nfrom flask import request, jsonify\nfrom flask_sqlalchemy import SQLAlchemy\n\nfrom config import create_app\nfrom model import Book\n\napp = create_app()\ndb = SQLAlchemy(app)\n\n\n# creating the rest endpoints\n\n# index\n# url = http:\/\/127.0.0.1:5000\/\n@app.route('\/', methods=['GET'])\ndef index():\n return {'message': 'Hello world!'}\n\n\n# save new book\n# url = http:\/\/127.0.0.1:5000\/book\n@app.route('\/book', methods=['POST'])\ndef save_book():\n if request.is_json:\n print('Saving new book')\n data = request.get_json()\n new_book = Book(title=data['title'], genre=data['genre'], author=data['author'], quantity=data['quantity'])\n db.session.add(new_book) # adding new data\n db.session.commit() # persisting the data\n db.session.refresh(new_book) # refresh the inserted object to get the primary key\n return {'message': f'Book {new_book.id} saved successfully'} # returning response\n else:\n return {'message': 'Payload is incorrect'}\n\n\n# get all books\n# url = http:\/\/127.0.0.1:5000\/books\n@app.route('\/books', methods=['GET'])\ndef get_books():\n print('Getting all books')\n books = Book.query.all()\n if not books:\n return {'items': [], 'count': 0, 'message': 'success'} # returning empty response\n else:\n result = [\n {\n 'id': b.id,\n 'title': b.title,\n 'genre': b.genre,\n 'author': b.author,\n 'quantity': b.quantity\n } for b in books]\n return {'items': result, 'count': len(books), 'message': 'success'} # returning response\n\n\n# get\/update\/book by id\n# url = http:\/\/127.0.0.1:5000\/book\/\n@app.route('\/book\/', methods=['GET', 'PUT', 'DELETE'])\ndef handle_book(book_id):\n print('Getting book id = {}'.format(book_id))\n book = Book.query.get_or_404(book_id)\n if request.method == 'GET':\n response = {\n 'id': book.id,\n 'title': book.title,\n 'genre': book.genre,\n 'author': book.author,\n 'quantity': book.quantity\n }\n return {'message': 'success', 'book': response} # returning response\n elif request.method == 'PUT':\n if request.is_json:\n print('Performing update')\n data = request.get_json()\n # updating the data\n db.session.query(Book).filter(Book.id == book_id).update({\n 'title': data['title'],\n 'genre': data['genre'],\n 'author': data['author'],\n 'quantity': data['quantity']\n })\n db.session.commit() # persisting the data\n return {'message': f'Book {book_id} updated successfully'} # returning response\n else:\n return {'message': 'Payload is incorrect'}\n elif request.method == 'DELETE':\n print('Performing delete')\n db.session.query(Book).filter(Book.id == book_id).delete() # deleting the data\n db.session.commit() # persisting the data\n return {'message': f'Book {book_id} deleted successfully'} # persisting the data\n\n\n# exception handler\n@app.errorhandler(405)\ndef method_not_allowed(e):\n return jsonify({'message': 'Request method not supported'}), 405\n\n\n# driver code\nif __name__ == '__main__':\n app.run(debug=False)\n<\/pre>\n4. Application Endpoints<\/h2>\n
app.py<\/code> is successfully started it would expose the following application endpoints which you can use for performing the different CRUD operations.<\/p>\n# save new book\n# url = http:\/\/127.0.0.1:5000\/book\n# sample request body\n# {\n# \"title\": \"{{$randomJobTitle}}\",\n# \"genre\": \"{{$randomBsBuzz}}\",\n# \"author\": \"{{$randomFullName}}\",\n# \"quantity\": \"{{$randomInt}}\"\n# }\n\n\n# get all books\n# url = http:\/\/127.0.0.1:5000\/books\n\n\n# get\/update\/book by id\n# url = http:\/\/127.0.0.1:5000\/book\/\n<\/pre>\n5. Summary<\/h2>\n
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6. Related articles<\/h2>\n