Python - PyQt Desktop App

• Setup
  • Hello World
• Signals
• Working with User Inputs
• Web Scraping
• Advanced UI Elements
• Advanced Layouts

Github Repository

Setup

pip install PyQt6

Hello World

Create a simple Layout in Qt6:

from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout
from PyQt6.QtWidgets import QLabel, QPushButton, QLineEdit

app = QApplication([])
window = QWidget()
window.setWindowTitle('PyQt6 Application')

layout = QVBoxLayout()

text = QLineEdit()

layout.addWidget(text)

window.setLayout(layout)
window.show()
app.exec()

Signals

State is exchanged in Qt by "signals":

def make_it_so():
    input_text = text.text()
    output_label.setText(input_text)

btn = QPushButton('Make it so!')
layout.addWidget(btn)
btn.clicked.connect(make_it_so)

output_label = QLabel('')
layout.addWidget(output_label)

When the button is clicked it triggers a function that then pushes the state - text input - of the input field to an label widget.

Working with User Inputs

Once we have the user input from our text widget we can add some functionality to it - for example turning input strings into URL-safe base64 representations:

from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout
from PyQt6.QtWidgets import QLabel, QPushButton, QLineEdit

import base64

# Add functions - what do you want to do with the user input

def to_base64():
    input_text = text_encode.text()
    encoded_bytes = base64.urlsafe_b64encode(input_text.encode("utf-8"))
    encoded_text = str(encoded_bytes, "utf-8")
    output_encode.setText("Encoded String: " + encoded_text)

def from_base64():
    input_text = text_decode.text()
    decoded_bytes = base64.urlsafe_b64decode(input_text.encode("utf-8"))
    decoded_text = str(decoded_bytes, "utf-8")
    output_decode.setText("Decoded String: " + decoded_text)

# App scaffolding

app = QApplication([])
window = QWidget()
window.setWindowTitle('base64 de/encoder')
layout = QVBoxLayout()

# Encode string to base64

text_encode = QLineEdit()
layout.addWidget(text_encode)

btn = QPushButton('base64 Encode')
layout.addWidget(btn)
btn.clicked.connect(to_base64)

output_encode = QLabel('')
layout.addWidget(output_encode)

# Decode string from base64

text_decode = QLineEdit()
layout.addWidget(text_decode)

btn = QPushButton('base64 Decode')
layout.addWidget(btn)
btn.clicked.connect(from_base64)

output_decode = QLabel('')
layout.addWidget(output_decode)

## Execute

window.setLayout(layout)
window.show()
app.exec()

Web Scraping

Using Beautiful Soup to scrape information from the web.

Calculate the price of an INSTAR camera by scraping the latest prize from the INSTAR web shop:

from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout
from PyQt6.QtWidgets import QLabel, QPushButton, QLineEdit

from bs4 import BeautifulSoup
import requests

def get_prize():
    url = f'https://www.instar.com/produkte/wlan-aussenkameras-poe-ip-kameras-wetterfeste-netzwerkkameras-outdoor-uberwachungskameras/in-9408-2k-serie-wlan-uberwachungskamera-ai-objekterkennung-apple-homekit-mqtt-sftp-nachtsicht/in-9408-2k-poe-weiss-ip-kamera.html'
    content = requests.get(url).text
    soup = BeautifulSoup(content, 'html.parser')
    prize = soup.find("span", class_="price").get_text()
    prize_intl = prize.replace(',', '.')
    prize_float = float(prize_intl[:-2])
    
    return prize_float


def calc_value():
    number = float(number_input.text())
    prize = get_prize()
    calculated_value = str(number * prize)
    number_output.setText(calculated_value)

# App scaffolding

app = QApplication([])
window = QWidget()
window.setWindowTitle('Price Calculator - INSTAR IN-9408 2k+')
layout = QVBoxLayout()

# Encode string to base64

number_input = QLineEdit()
layout.addWidget(number_input)

btn = QPushButton('Get Price')
layout.addWidget(btn)
btn.clicked.connect(calc_value)

number_output = QLabel('')
layout.addWidget(number_output)

## Execute

window.setLayout(layout)
window.show()
app.exec()

Advanced UI Elements

Using Dropdown menus:

currencies = ['USD','EUR','GBP','CNY']

select_inCurrency = QComboBox()
select_inCurrency.addItems(currencies)
layout.addWidget(select_inCurrency)

select_outCurrency = QComboBox()
select_outCurrency.addItems(currencies)
layout.addWidget(select_outCurrency)

Advanced Layouts

from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout, QHBoxLayout
from PyQt6.QtWidgets import QLabel, QPushButton, QLineEdit, QComboBox

from bs4 import BeautifulSoup
import requests

def get_conversion(in_currency, out_currency):
    url = f'https://www.x-rates.com/calculator/?from={in_currency}&to={out_currency}&amount=1'
    content = requests.get(url).text
    soup = BeautifulSoup(content, 'html.parser')
    rate = soup.find("span", class_="ccOutputRslt").get_text()
    rate_float = float(rate[:-4])

    return rate_float

def calc_value():
    number = float(number_input.text())
    in_currency = select_inCurrency.currentText()
    out_currency = select_outCurrency.currentText()
    rate = get_conversion(in_currency, out_currency)
    calculated_value = str(number * rate)
    message = f'{number} {in_currency} is {calculated_value} {out_currency}'
    number_output.setText(message)

# App scaffolding

app = QApplication([])
window = QWidget()
window.setWindowTitle('Currency Converter')

layoutMain = QVBoxLayout()
layoutContainer = QHBoxLayout()
layoutMain.addLayout(layoutContainer)

layoutLeftBox = QVBoxLayout()
layoutContainer.addLayout(layoutLeftBox)
layoutRightBox = QVBoxLayout()
layoutContainer.addLayout(layoutRightBox)


# Select Currencies

currencies = ['USD','EUR','GBP','CNY']

select_inCurrency = QComboBox()
select_inCurrency.addItems(currencies)
layoutLeftBox.addWidget(select_inCurrency)

select_outCurrency = QComboBox()
select_outCurrency.addItems(currencies)
layoutLeftBox.addWidget(select_outCurrency)

# Convert to Target Currency

number_input = QLineEdit()
layoutRightBox.addWidget(number_input)

btn = QPushButton('Convert')
layoutMain.addWidget(btn)
btn.clicked.connect(calc_value)

number_output = QLabel('')
layoutRightBox.addWidget(number_output)

## Execute

window.setLayout(layoutMain)
window.show()
app.exec()