How to execute silent print of QR codes in python

Question

I have created a personal POS application which is sending a JSON object via HTTP Request. UI of the POS app:

When buttons Pay or Dispense are clicked then a json object is sent via POST method. I have created a draft HTTP server in python just to receive the sent data. Here is the code:

from http.server import BaseHTTPRequestHandler, HTTPServer


hostName = "localhost"
serverPort = 49231


class MyServer(BaseHTTPRequestHandler):

    def do_POST(self):
        print(self.headers)
        content_len = int(self.headers.get('content-length', 0))
        post_body = self.rfile.read(content_len)
        post_body = post_body.decode('utf-8')


if __name__ == "__main__":
    webServer = HTTPServer((hostName, serverPort), MyServer)
    print("Server started http://%s:%s" % (hostName, serverPort))

    try:
      webServer.serve_forever()
    except KeyboardInterrupt:
        webServer.server_close()
        print("Server stopped.")

In post_body variable I have the json sent from the POS app. My idea was to encode the json string into a qr code then print the qr code so as to take the paper with the qr code printed and scan it. I used the qrcode module to create the QR code. My simple function to generate QR code from string:

import tempfile
import qrcode


def generate_qr(qr_input):
    with tempfile.NamedTemporaryFile(delete=False, suffix='.png') as tmpfile:
        qr = qrcode.make(qr_input)
        qr.save(tmpfile, qr.format, quality=100)
        return open(tmpfile.name, 'rb'), 'image/png'

For the silent print I found this, where with the help of win32api and win32print modules, we can execute a silent print. My problem is that win32api.ShellExecute documentation says that we need to have a document file in order to execute properly this method. Now my custom generator of QR code is returning a tuple with the temp file. I am using also tempfile module, as I don't want every time that the button is clicked to create a new file containing a QR code. My question is how can I generate a document file from a temp PNG file in python?

Finally, as this code is produced for a university project, any new idea on how to execute silent print would be welcome.

My complete code:

import tempfile
import win32api
import win32print
from http.server import BaseHTTPRequestHandler, HTTPServer
import qrcode

hostName = "localhost"
serverPort = 49231

def generate_qr(qr_input):
    with tempfile.NamedTemporaryFile(delete=False, suffix='.png') as tmpfile:
        qr = qrcode.make(qr_input)
        qr.save(tmpfile, qr.format, quality=100)
        return open(tmpfile.name, 'rb'), 'image/png'


class MyServer(BaseHTTPRequestHandler):

    def do_POST(self):
        print(self.headers)
        # print_qr = {}
        content_len = int(self.headers.get('content-length', 0))
        post_body = self.rfile.read(content_len)
        post_body = post_body.decode('utf-8')
        print(post_body)
        print_qr = generate_qr(post_body)
        win32api.ShellExecute(
            0,
            'print',
            print_qr,
            '"%s"' % win32print.GetDefaultPrinter(),
            '.',
            0
        )






if __name__ == "__main__":
    webServer = HTTPServer((hostName, serverPort), MyServer)
    print("Server started http://%s:%s" % (hostName, serverPort))

    try:
      webServer.serve_forever()
    except KeyboardInterrupt:
        webServer.server_close()
        print("Server stopped.")

Answer 1

Try and read carefully the win32api and all your questions will be solved