{"id":1564,"date":"2019-05-12T14:32:54","date_gmt":"2019-05-12T06:32:54","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=1564"},"modified":"2020-05-12T10:47:08","modified_gmt":"2020-05-12T02:47:08","slug":"how-to-create-an-api-endpoint-that-generates-a-qr-code-image-with-python-3-flask-restplus-and-python-qrcode","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-create-an-api-endpoint-that-generates-a-qr-code-image-with-python-3-flask-restplus-and-python-qrcode\/","title":{"rendered":"How to create an API endpoint that generates a QR Code image, with Python 3 Flask-RESTPlus and python-qrcode"},"content":{"rendered":"

When you have an API endpoint that generates a QR Code image, another device with a QR Code scanner will be able to get the encoded value to perform some action. For example, WhatsApp web generates a QR Code image that encodes a code for WhatsApp app to sign in the user.<\/p>\n

So how can you create an API endpoint that generates a QR Code image? With this in mind, let's look at how we can do so with Python 3 Flask-RESTPlus<\/a> and python-qrcode<\/a>.<\/p>\n

Specifying the Python 3 dependencies for creating an API endpoint that generates a QR Code image<\/h2>\n

First, let's proceed with installing the Python 3 dependencies for creating an API endpoint that generates a QR Code image into your Python 3 environment. In order to do so, create a requirements.txt<\/code> file with the following content:<\/p>\n

\r\nflask-restplus==0.12.1\r\nPillow==6.0.0\r\nqrcode==6.1\r\n<\/pre>\n
As shown above, we will need a href=\"https:\/\/flask-restplus.readthedocs.io\/en\/stable\/\" rel=\"noopener\" target=\"_blank\">flask-restplus<\/a>, Pillow<\/a> and qrcode<\/a> for creating an API endpoint that generates a QR Code image.<\/p>\n
Creating the Python 3 code for creating an API endpoint that generates a QR Code image<\/h2>\n
In order to keep things simple, let's create the Python 3 codes as a single source file and name it as run_app.py<\/code>:<\/p>\n
\r\nfrom flask import Flask, Blueprint, request, send_file\r\nfrom flask_restplus import Api, Namespace, Resource, fields\r\nfrom io import BytesIO\r\n\r\nimport os, qrcode\r\n\r\n# Create Flask app\r\napp = Flask(__name__)\r\n\r\n# Associate Api with Blueprint\r\napi_blueprint = Blueprint('API', __name__)\r\napi = Api(api_blueprint,\r\n    title='Api for QR code app',\r\n    version='1.0',\r\n    description='This is an API for QR code app',\r\n    # All API metadatas\r\n)\r\n\r\n# Create namespace for containing Qr Code related operations\r\nqrcode_namespace = Namespace('QrCode', description='Qr code related operations')\r\n# Specify uri of qrcode namespace as \/qrcode\r\napi.add_namespace(qrcode_namespace, path='\/qrcode')\r\n# Specify uri of api blueprint as \/api\r\napp.register_blueprint(api_blueprint, url_prefix='\/api')\r\n\r\n# Define input model\r\nqrcode_creation_input = qrcode_namespace.model('QRCode creation Input', {\r\n    'value': fields.String(required=True, description='The value that is supposed to be encoded into qrcode'),\r\n})\r\n\r\n\r\n# Define API endpoint for creating Qr Code image\r\n@qrcode_namespace.route('\/')\r\n@qrcode_namespace.doc('Creates a QRCode image based on a string value.')\r\nclass QrCodeRoot(Resource):\r\n\r\n    @qrcode_namespace.expect(qrcode_creation_input)\r\n    @qrcode_namespace.produces(['image\/png'])\r\n    @qrcode_namespace.response(200, description='Return QR Code png image file.')\r\n    @qrcode_namespace.response(400, description='Invalid input provided.')\r\n    def post(self):\r\n\r\n        # Get value to encode into QR Code\r\n        json_input = request.get_json()\r\n        value_to_turn_into_qrcode = json_input['value']\r\n\r\n        # Create qr code image and return it as HTTP response\r\n        pil_img = qrcode.make(value_to_turn_into_qrcode)\r\n        img_io = BytesIO()\r\n        pil_img.save(img_io, 'PNG')\r\n        img_io.seek(0)\r\n        return send_file(img_io, mimetype='image\/png')\r\n\r\n\r\nif __name__ == '__main__':\r\n    port = int(os.getenv("PORT", "5678"))\r\n    app.run(host='0.0.0.0', port=port)\r\n<\/pre>\n
Understanding the Python 3 code for creating an API endpoint that generates a QR Code image<\/h2>\n
In case you are wondering what the previous Python 3 code does, this section explains the code by parts.<\/p>\n
Importing the necessary dependencies for creating an API endpoint that generates a QR Code image<\/h3>\n
First, we import the necessary dependencies for creating an API endpoint that generates a QR code image:<\/p>\n
\r\nfrom flask import Flask, Blueprint, request, send_file\r\nfrom flask_restplus import Api, Namespace, Resource, fields\r\nfrom io import BytesIO\r\n\r\nimport os, qrcode\r\n<\/pre>\n
Wiring flask_restplus with Flask to realise the uri for creating an API endpoint that generates a QR Code image<\/h3>\n
After we had imported the necessary dependencies, we then proceed to wire Flask Restplus with Flask to realise the url for creating an API endpoint that generates a QR Code image:<\/p>\n
\r\n# Create Flask app\r\napp = Flask(__name__)\r\n\r\n# Associate Api with Blueprint\r\napi_blueprint = Blueprint('API', __name__)\r\napi = Api(api_blueprint,\r\n    title='Api for QR code app',\r\n    version='1.0',\r\n    description='This is an API for QR code app',\r\n    # All API metadatas\r\n)\r\n\r\n# Create namespace for containing Qr Code related operations\r\nqrcode_namespace = Namespace('QrCode', description='Qr code related operations')\r\n# Specify uri of qrcode namespace as \/qrcode\r\napi.add_namespace(qrcode_namespace, path='\/qrcode')\r\n# Specify uri of api blueprint as \/api\r\napp.register_blueprint(api_blueprint, url_prefix='\/api')\r\n<\/pre>\n
After the script ran the above codes, we will have a swagger documentation page available via \/api<\/code>. In addition to that, QR Code related API endpoints can be made available via \/api\/qrcode<\/code> through the various decorator functions in qrcode_namespace<\/code>.<\/p>\n
Defining the expected input for the API endpoint that generates a QR Code image<\/h3>\n
Next, we then define the input model for the API endpoint that generates a QR Code image:<\/p>\n
\r\n# Define input model\r\nqrcode_creation_input = qrcode_namespace.model('QRCode creation Input', {\r\n    'value': fields.String(required=True, description='The value that is supposed to be encoded into qrcode'),\r\n})\r\n<\/pre>\n
Given that, we can then tell Flask RESTPlus to ensure that any HTTP request<\/a> made to the API endpoint that generates a QR Code image adheres to the following JSON format:<\/p>\n
\r\n{\r\n  "value": "string to encode as QR code image"\r\n}\r\n<\/pre>\n
Defining the API endpoint that generates a QR Code image<\/h3>\n
Given that we have the input model and namespace, we can then define the API endpoint that generates a QR Code image:<\/p>\n
\r\n# Define API endpoint for creating Qr Code image\r\n@qrcode_namespace.route('\/')\r\n@qrcode_namespace.doc('Creates a QRCode image based on a string value.')\r\nclass QrCodeRoot(Resource):\r\n \r\n    @qrcode_namespace.expect(qrcode_creation_input)\r\n    @qrcode_namespace.produces(['image\/png'])\r\n    @qrcode_namespace.response(200, description='Return QR Code png image file.')\r\n    @qrcode_namespace.response(400, description='Invalid input provided.')\r\n    def post(self):\r\n \r\n        # Get value to encode into QR Code\r\n        json_input = request.get_json()\r\n        value_to_turn_into_qrcode = json_input['value']\r\n \r\n        # Create qr code image and return it as HTTP response\r\n        pil_img = qrcode.make(value_to_turn_into_qrcode)\r\n        img_io = BytesIO()\r\n        pil_img.save(img_io, 'PNG')\r\n        img_io.seek(0)\r\n        return send_file(img_io, mimetype='image\/png')\r\n<\/pre>\n
In the above code, we defined a HTTP post request handler made to \/api\/qrcode<\/code>. Inside the handler function, we first get the value to encode into QR code image.<\/p>\n
After that, we use qrcode.make<\/code> to get a Pillow instance that represents the encoded QR Code image. Given that, we then use an instance of BytesIO<\/code><\/a> to hold the binary data of that QR Code image.<\/p>\n
Once we have done so, we then use the send_file<\/a> function to return the contents of that BytesIO instance as a HTTP response<\/a>.<\/p>\n
Running the Flask application with an API endpoint that generates a QR Code image<\/h3>\n
At the end of the script, we run the Flask application with the following code:<\/p>\n
\r\nif __name__ == '__main__':\r\n    port = int(os.getenv("PORT", "5678"))\r\n    app.run(host='0.0.0.0', port=port)\r\n<\/pre>\n
The above code first check if the script is being run directly. If that is the case, it then checks if any port is provided as an environment variable named PORT<\/strong>. If no port is given, the port to run the Flask application is set to 5678<\/strong>.<\/p>\n
Given that port number, we then run the Flask application.<\/p>\n
Running example program<\/h2>\n
At this point in time, we will have created the following files:<\/p>\n