from PyQt5.QtWidgets import (QApplication, QWidget, QVBoxLayout, 
                            QLabel, QLineEdit, QPushButton)

class ConverterApp(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Temperature Converter")
        self.setup_ui()
    
    def setup_ui(self):
        # Create widgets
        self.celsius_input = QLineEdit()
        self.fahrenheit_input = QLineEdit()
        self.convert_btn = QPushButton("Convert")
        self.result_label = QLabel("Enter temperature to convert")
        
        # Set up layout
        layout = QVBoxLayout()
        layout.addWidget(QLabel("Celsius:"))
        layout.addWidget(self.celsius_input)
        layout.addWidget(QLabel("Fahrenheit:"))
        layout.addWidget(self.fahrenheit_input)
        layout.addWidget(self.convert_btn)
        layout.addWidget(self.result_label)
        
        # Connect button click
        self.convert_btn.clicked.connect(self.convert)
        
        self.setLayout(layout)
    
    def convert(self):
        try:
            if self.celsius_input.text():
                # Celsius to Fahrenheit
                celsius = float(self.celsius_input.text())
                fahrenheit = (celsius * 9/5) + 32
                self.fahrenheit_input.setText(f"{fahrenheit:.2f}")
                self.result_label.setText("Conversion complete!")
            elif self.fahrenheit_input.text():
                # Fahrenheit to Celsius
                fahrenheit = float(self.fahrenheit_input.text())
                celsius = (fahrenheit - 32) * 5/9
                self.celsius_input.setText(f"{celsius:.2f}")
                self.result_label.setText("Conversion complete!")
        except ValueError:
            self.result_label.setText("Please enter a valid number!")

if __name__ == "__main__":
    app = QApplication([])
    window = ConverterApp()
    window.show()
    app.exec_()

---

## 🔹 PyQt5 Designer Tool
Qt Designer lets you create UIs visually:

1. Launch Designer:

   pyqt5-tools designer
   

2. Design your interface (saves as .ui file)
3. Convert to Python code:

   pyuic5 input.ui -o output.py
   

Example Usage:

from PyQt5 import uic
class MyApp(QMainWindow):
    def __init__(self):
        super().__init__()
        uic.loadUi('design.ui', self)  # Load UI file

---

## 🔹 Event Handling Basics
PyQt5 uses signals and slots for interactivity:

# Connecting signals to slots
button.clicked.connect(self.on_button_click)
checkbox.stateChanged.connect(self.on_checkbox_change)
line_edit.textChanged.connect(self.on_text_change)

# Example slot methods
def on_button_click(self):
    print("Button clicked!")

def on_checkbox_change(self, state):
    print("Checkbox state:", state)

def on_text_change(self, text):
    print("Text changed to:", text)

---

## 🔹 Best Practices for Beginners
1. Organize code in classes/methods
2. Use layouts instead of absolute positioning
3. Name widgets clearly (e.g., self.login_btn)
4. Separate UI code from business logic
5. Handle errors gracefully in event handlers

---

### 📌 What's Next?
In Part 2, we'll cover:
➡️ Advanced Widgets (Tables, Trees, Tabs)
➡️ Custom Signals
➡️ Styling with QSS
➡️ Multiple Windows

#PyQt5Tutorial #GUIPython #LearnToCode 🚀

Practice Exercise:
1. Create a simple calculator app
2. Build a text editor with save/load buttons
3. Make a color picker that changes window background