Topic: Data Structures – Trees – Part 4 of 4: Advanced Trees – Red-Black Trees and Trie

---

### 1. Introduction

This part covers two advanced and widely used tree data structures:

• Red-Black Trees – balanced search trees
• Trie (Prefix Tree) – efficient string storage and retrieval

---

### 2. Red-Black Trees (RBT)

---

#### What is a Red-Black Tree?

A Red-Black Tree is a self-balancing Binary Search Tree with extra color property:

* Each node is either red or black
* Root is always black
* Red nodes cannot have red children (no two reds in a row)
* Every path from root to leaves has the same number of black nodes (black-height)

---

#### Why Red-Black Trees?

* Guarantees O(log n) time for insert, delete, and search
* Slightly less rigid balancing than AVL but faster insertion/deletion
* Used in many libraries (e.g., C++ STL map/set)

---

#### Key Properties Recap

1. Every node is red or black
2. Root is black
3. Red nodes have black children
4. Every path from root to null leaves contains same black nodes count

---

#### Basic Operations

* Insertions and deletions are followed by color adjustments and rotations
* Ensures tree remains balanced with Red-Black properties intact

---

### 3. Trie (Prefix Tree)

---

#### What is a Trie?

A Trie is a tree-like data structure used to store a dynamic set of strings, where:

* Each node represents a character
* Path from root to leaf forms a word
* Used for prefix searches efficiently

---

#### Why Use a Trie?

• Fast lookup for words and prefixes
• Auto-complete features
• Spell checking
• IP routing (longest prefix matching)

---

#### Trie Node Structure (Python)

class TrieNode:
    def __init__(self):
        self.children = {}
        self.is_end_of_word = False

---

#### Basic Operations

Insert Word:

def insert(root, word):
    node = root
    for char in word:
        if char not in node.children:
            node.children[char] = TrieNode()
        node = node.children[char]
    node.is_end_of_word = True

Search Word:

def search(root, word):
    node = root
    for char in word:
        if char not in node.children:
            return False
        node = node.children[char]
    return node.is_end_of_word

---

### 4. Example Usage of Trie

root = TrieNode()
insert(root, "hello")
insert(root, "helium")

print(search(root, "hello"))  # True
print(search(root, "hel"))    # False (prefix only)

---

### 5. Advantages and Disadvantages

| Data Structure | Advantages | Disadvantages |
| -------------- | -------------------------------------- | ------------------------------- |
| Red-Black Tree | Balanced, efficient search and update | Complex implementation |
| Trie | Fast prefix search and auto-completion | Memory-heavy with many children |

---

### 6. Summary

* Red-Black Trees and AVL Trees both keep BSTs balanced but with different balancing rules
* Tries are specialized for string data, enabling efficient prefix operations
* Both structures are essential for advanced algorithms and systems

---

### 7. Exercise

• Implement basic Red-Black Tree insertion (research needed)
• Implement delete operation in Trie
• Use Trie to implement a simple autocomplete function
• Compare search time for BST vs Trie on string data sets

---

#DSA #RedBlackTree #Trie #AdvancedTrees #DataStructures #Python

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Topic: Data Structures – Trees – Top 15 Interview Questions with Answers

---

### 1. What is a tree data structure?

A hierarchical structure with nodes connected by edges, having a root node and child nodes with no cycles.

---

### 2. What is the difference between binary tree and binary search tree (BST)?

A binary tree allows up to two children per node; BST maintains order where left child < node < right child.

---

### 3. What are the types of binary trees?

Full, perfect, complete, skewed (left/right), and balanced binary trees.

---

### 4. Explain tree traversal methods.

Inorder (LNR), Preorder (NLR), Postorder (LRN), and Level Order (BFS).

---

### 5. What is a balanced tree? Why is it important?

A tree where the height difference between left and right subtrees is minimal to ensure O(log n) operations.

---

### 6. What is an AVL tree?

A self-balancing BST maintaining balance factor (-1, 0, 1) with rotations to balance after insert/delete.

---

### 7. What are rotations in AVL trees?

Operations (Left, Right, Left-Right, Right-Left) used to rebalance the tree after insertion or deletion.

---

### 8. What is a Red-Black Tree?

A balanced BST with red/black nodes ensuring balance via color rules, offering O(log n) operations.

---

### 9. How does a Trie work?

A tree structure used for storing strings, where nodes represent characters, allowing fast prefix searches.

---

### 10. What is the height of a binary tree?

The number of edges on the longest path from root to a leaf node.

---

### 11. How do you find the lowest common ancestor (LCA) of two nodes?

By traversing from root, checking if nodes lie in different subtrees, or by storing parent pointers.

---

### 12. What is the difference between DFS and BFS on trees?

DFS explores as far as possible along branches; BFS explores neighbors level by level.

---

### 13. How do you detect if a binary tree is a BST?

Check if inorder traversal yields a sorted sequence or verify node values within valid ranges recursively.

---

### 14. What are leaf nodes?

Nodes with no children.

---

### 15. How do you calculate the number of nodes in a complete binary tree?

Using the formula: number\_of\_nodes = 2^(height + 1) - 1 (if perfect), else traverse and count.

---

### Exercise

Write functions for inorder, preorder, postorder traversals, check if tree is BST, and find LCA of two nodes.

---

#DSA #Trees #InterviewQuestions #BinaryTrees #Python #Algorithms

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Topic: Python – Create IP Address Tracker GUI using Tkinter

---

### What You'll Build

A desktop app that allows the user to:

• Enter an IP address or domain
• Fetch geolocation data (country, city, ISP, etc.)
• Display it in a user-friendly Tkinter GUI

We'll use the requests library and a free API like ip-api.com.

---

### Step-by-Step Code

import tkinter as tk
from tkinter import messagebox
import requests

# Function to fetch IP information
def track_ip():
    ip = entry.get().strip()
    if not ip:
        messagebox.showwarning("Input Error", "Please enter an IP or domain.")
        return

    try:
        url = f"http://ip-api.com/json/{ip}"
        response = requests.get(url)
        data = response.json()

        if data["status"] == "fail":
            messagebox.showerror("Error", data["message"])
            return

        # Show info
        result_text.set(
            f"IP: {data['query']}\n"
            f"Country: {data['country']}\n"
            f"Region: {data['regionName']}\n"
            f"City: {data['city']}\n"
            f"ZIP: {data['zip']}\n"
            f"ISP: {data['isp']}\n"
            f"Timezone: {data['timezone']}\n"
            f"Latitude: {data['lat']}\n"
            f"Longitude: {data['lon']}"
        )

    except Exception as e:
        messagebox.showerror("Error", str(e))

# GUI Setup
app = tk.Tk()
app.noscript("IP Tracker")
app.geometry("400x400")
app.resizable(False, False)

# Widgets
tk.Label(app, text="Enter IP Address or Domain:", font=("Arial", 12)).pack(pady=10)

entry = tk.Entry(app, width=40, font=("Arial", 12))
entry.pack()

tk.Button(app, text="Track IP", command=track_ip, font=("Arial", 12)).pack(pady=10)

result_text = tk.StringVar()
result_label = tk.Label(app, textvariable=result_text, justify="left", font=("Courier", 10))
result_label.pack(pady=10)

app.mainloop()

---

### Requirements

Install the requests library if not already installed:

pip install requests

---

### Exercise

• Enhance the app to export the result to a .txt or .csv file
• Add a map preview using a web view or link to Google Maps
• Add dark mode toggle for the GUI

---

#Python #Tkinter #IPTracker #Networking #GUI #DesktopApp

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Topic: Python Functions – Part 1 of 3: Basics, Syntax, and Parameters (Long Lesson)

---

### 1. What is a Function in Python?

A function is a reusable block of code that performs a specific task. Functions help:

• Avoid code duplication
• Improve code readability
• Enable modular programming

---

### 2. Why Use Functions?

• Reusability – Write once, use many times
• Modularity – Split large tasks into smaller blocks
• Debuggability – Easier to test/debug small units
• Abstraction – Hide complex logic behind a name

---

### 3. Function Syntax

def function_name(parameters):
    # block of code
    return result

---

### 4. Creating a Simple Function

def greet():
    print("Hello, welcome to Python functions!")
    
greet()  # Calling the function

---

### 5. Function with Parameters

def greet_user(name):
    print(f"Hello, {name}!")

greet_user("Hussein")

---

### 6. Function with Return Value

def add(a, b):
    return a + b

result = add(10, 5)
print(result)  # Output: 15

---

### 7. Positional vs Keyword Arguments

def student_info(name, age):
    print(f"Name: {name}, Age: {age}")

student_info("Ali", 22)  # Positional
student_info(age=22, name="Ali")  # Keyword

---

### 8. Default Parameter Values

def greet(name="Guest"):
    print(f"Hello, {name}!")

greet()            # Output: Hello, Guest!
greet("Hussein")   # Output: Hello, Hussein!

---

### 9. Variable Number of Arguments

#### \*args – Multiple positional arguments:

def sum_all(*numbers):
    total = 0
    for num in numbers:
        total += num
    return total

print(sum_all(1, 2, 3, 4))  # Output: 10

#### \*\*kwargs – Multiple keyword arguments:

def print_details(**info):
    for key, value in info.items():
        print(f"{key}: {value}")

print_details(name="Ali", age=24, country="Egypt")

---

### **10. Scope of Variables**

#### Local vs Global Variables

x = "global"

def func():
    x = "local"
    print(x)

func()     # Output: local
print(x)   # Output: global

Use global keyword if you want to modify a global variable inside a function.

---

### 11. Docstrings (Function Documentation)

def square(n):
    """Returns the square of a number."""
    return n * n

print(square.__doc__)  # Output: Returns the square of a number.

---

### 12. Best Practices

• Use denoscriptive names for functions
• Keep functions short and focused
• Avoid side effects unless needed
• Add docstrings for documentation

---

### Exercise

• Create a function that takes a list and returns the average
• Create a function that takes any number of scores and returns the highest
• Create a function with default arguments for greeting a user by name and language

---

#Python #Functions #CodingBasics #ModularProgramming #CodeReuse #PythonBeginners

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# 📚 PyQt5 Tutorial - Part 1/6: Introduction to GUI Programming
#PyQt5 #Python #GUI #BeginnerFriendly #Qt

Welcome to Part 1 of our comprehensive PyQt5 series! This lesson will introduce you to GUI development with Python and PyQt5, perfect for beginners.

---

## 🔹 What is PyQt5?
PyQt5 is a set of Python bindings for Qt (a powerful C++ GUI framework). It lets you create:
- Desktop applications
- Cross-platform GUIs
- Professional-looking interfaces
- Apps with databases, networking, and multimedia

Key Features:
✔️ 620+ classes
✔️ 6,000+ functions
✔️ Windows, Mac, Linux support
✔️ Open-source (GPL/commercial licenses)

---

## 🔹 Installation
Install PyQt5 and tools:

pip install PyQt5 PyQt5-tools

Verify Installation:

import PyQt5
print(PyQt5.__version__)  # Should show version like 5.15.4

---

## 🔹 Your First PyQt5 App
Let's create a simple window:

import sys
from PyQt5.QtWidgets import QApplication, QLabel, QWidget

# 1. Create the application object
app = QApplication(sys.argv)

# 2. Create main window
window = QWidget()
window.setWindowTitle("My First App")
window.setGeometry(100, 100, 400, 200)  # x, y, width, height

# 3. Add a label
label = QLabel("Hello PyQt5!", parent=window)
label.move(150, 80)  # x, y position

# 4. Show the window
window.show()

# 5. Run the application
sys.exit(app.exec_())

Code Breakdown:
1. QApplication: Manages app control flow
2. QWidget: Base class for all UI objects
3. QLabel: Displays text/images
4. exec_(): Starts the event loop

---

## 🔹 Core PyQt5 Components
### 1. Main Window Types
| Class | Purpose |
|-------|---------|
| QWidget | Basic empty window |
| QMainWindow | With menu bar, status bar, toolbars |
| QDialog | Popup dialog windows |

### 2. Common Widgets

from PyQt5.QtWidgets import (
    QPushButton,  # Clickable button
    QLineEdit,    # Single-line text input
    QTextEdit,    # Multi-line text area
    QCheckBox,    # Toggle option
    QRadioButton, # Exclusive choice
    QComboBox,    # Dropdown menu
    QSlider       # Value selector
)

### 3. Layout Managers

from PyQt5.QtWidgets import (
    QVBoxLayout,  # Vertical arrangement
    QHBoxLayout,  # Horizontal arrangement
    QGridLayout   # Grid arrangement
)

---

## 🔹 Creating a Functional App
Let's build a temperature converter:

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

# 📚 PyQt5 Tutorial - Part 2/6: Advanced Widgets & Customization
#PyQt5 #PythonGUI #AdvancedWidgets #QSS #SignalsSlots

Welcome to Part 2 of our PyQt5 series! This in-depth lesson covers advanced widgets, custom styling, multi-window applications, and professional patterns.

---

## 🔹 Advanced Widgets Overview
### 1. Tabbed Interfaces (QTabWidget)

from PyQt5.QtWidgets import QTabWidget, QTextEdit, QWidget

class TabDemo(QWidget):
    def __init__(self):
        super().__init__()
        
        tabs = QTabWidget()
        
        # Tab 1: Text Editor
        tab1 = QWidget()
        text_edit = QTextEdit()
        tab1_layout = QVBoxLayout()
        tab1_layout.addWidget(text_edit)
        tab1.setLayout(tab1_layout)
        
        # Tab 2: Settings
        tab2 = QWidget()
        tab2_layout = QVBoxLayout()
        tab2_layout.addWidget(QLabel("Settings Panel"))
        tab2.setLayout(tab2_layout)
        
        tabs.addTab(tab1, "Editor")
        tabs.addTab(tab2, "Settings")
        
        main_layout = QVBoxLayout()
        main_layout.addWidget(tabs)
        self.setLayout(main_layout)

### 2. Tree Widget (QTreeWidget)

def setup_file_tree(self):
    tree = QTreeWidget()
    tree.setHeaderLabels(["Name", "Size", "Type"])
    
    # Add parent items
    root = QTreeWidgetItem(tree)
    root.setText(0, "Project Root")
    
    # Add children
    for file in ["main.py", "config.ini", "README.md"]:
        child = QTreeWidgetItem(root)
        child.setText(0, file)
        child.setText(1, "10 KB")
        child.setText(2, "Python" if file.endswith(".py") else "Text")
    
    tree.expandAll()
    return tree

### 3. Table Widget (QTableWidget)

def setup_data_table(self):
    table = QTableWidget(5, 3)  # Rows, columns
    table.setHorizontalHeaderLabels(["ID", "Name", "Status"])
    
    sample_data = [
        [101, "Product A", "Active"],
        [102, "Product B", "Inactive"],
        [103, "Product C", "Pending"]
    ]
    
    for row, data in enumerate(sample_data):
        for col, text in enumerate(data):
            item = QTableWidgetItem(str(text))
            table.setItem(row, col, item)
    
    table.resizeColumnsToContents()
    return table

---

## 🔹 Custom Signals & Slots
### 1. Creating Custom Signals

from PyQt5.QtCore import pyqtSignal, QObject

class Worker(QObject):
    progress_changed = pyqtSignal(int)
    task_completed = pyqtSignal(str)
    
    def run_task(self):
        for i in range(1, 101):
            time.sleep(0.05)
            self.progress_changed.emit(i)
        self.task_completed.emit("Task finished!")

### 2. Advanced Signal-Slot Connections

# Multiple signals to single slot
button1.clicked.connect(self.handle_click)
button2.clicked.connect(self.handle_click)

# Signal with arguments
self.worker.progress_changed.connect(self.update_progress_bar)

# Lambda slots
button.clicked.connect(lambda: self.process_data(param1, param2))

# Slot decorator
@pyqtSlot()
def on_button_click(self):
    print("Button clicked!")

---

## 🔹 Styling with Qt Style Sheets (QSS)
### 1. Basic Styling

app.setStyleSheet("""
    QPushButton {
        background-color: #4CAF50;
        border: none;
        color: white;
        padding: 8px 16px;
        font-size: 14px;
    }
    QPushButton:hover {
        background-color: #45a049;
    }
    QLineEdit {
        padding: 5px;
        border: 1px solid #ccc;
        border-radius: 3px;
    }
""")

### 2. Advanced Selectors

/* Style only buttons in the toolbar */
QToolBar QPushButton {
    min-width: 80px;
}

/* Style checked checkboxes differently */
QCheckBox:checked {
    color: #0085FF;
}

/* Style odd/even table rows */
QTableView::item:alternate {
    background: #f0f0f0;
}

### 3. Dynamic Style Changes

# Change style programmatically
button.setStyleSheet("""
    QPushButton {
        background-color: red;
        font-weight: bold;
    }
""")

# Reset to default
button.setStyleSheet("")

---

## 🔹 Multi-Window Applications
### 1. Creating Secondary Windows

class SettingsWindow(QDialog):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Settings")
        layout = QVBoxLayout()
        layout.addWidget(QLabel("Application Settings"))
        self.setLayout(layout)

# In main window:
def show_settings(self):
    settings = SettingsWindow()
    settings.exec_()  # Modal dialog
    # OR settings.show() for non-modal

### 2. Window Communication

# Main window with signal
class MainWindow(QMainWindow):
    settings_changed = pyqtSignal(dict)
    
    def open_settings(self):
        dialog = SettingsDialog(self)  # Pass parent
        if dialog.exec_():
            self.settings_changed.emit(dialog.get_settings())

# Settings dialog
class SettingsDialog(QDialog):
    def __init__(self, parent=None):
        super().__init__(parent)
        # ... setup UI ...
    
    def get_settings(self):
        return {"theme": self.theme_combo.currentText()}

---

## 🔹 Model-View Architecture
### 1. QListView with StringListModel

model = QStringListModel()
model.setStringList(["Item 1", "Item 2", "Item 3"])

list_view = QListView()
list_view.setModel(model)

# Add items
model.insertRow(model.rowCount())
model.setData(model.index(model.rowCount()-1), "New Item")

### 2. Custom Table Model

class CustomTableModel(QAbstractTableModel):
    def __init__(self, data):
        super().__init__()
        self._data = data
    
    def rowCount(self, parent=None):
        return len(self._data)
    
    def columnCount(self, parent=None):
        return len(self._data[0]) if self._data else 0
    
    def data(self, index, role=Qt.DisplayRole):
        if role == Qt.DisplayRole:
            return str(self._data[index.row()][index.column()])
        return None

# Usage
data = [[1, "Alice"], [2, "Bob"], [3, "Charlie"]]
model = CustomTableModel(data)
table = QTableView()
table.setModel(model)

---

## 🔹 Practical Example: Text Editor

class TextEditor(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setup_ui()
        self.setup_menu()
    
    def setup_ui(self):
        self.text_edit = QTextEdit()
        self.setCentralWidget(self.text_edit)
        
        # Status bar
        self.statusBar().showMessage("Ready")
        
        # Toolbar
        toolbar = self.addToolBar("Tools")
        save_act = QAction(QIcon("save.png"), "Save", self)
        save_act.triggered.connect(self.save_file)
        toolbar.addAction(save_act)
    
    def setup_menu(self):
        menubar = self.menuBar()
        
        # File menu
        file_menu = menubar.addMenu("File")
        
        open_act = QAction("Open", self)
        open_act.triggered.connect(self.open_file)
        file_menu.addAction(open_act)
        
        # Edit menu
        edit_menu = menubar.addMenu("Edit")
        edit_menu.addAction("Copy", self.text_edit.copy)
        edit_menu.addAction("Paste", self.text_edit.paste)
    
    def open_file(self):
        path, _ = QFileDialog.getOpenFileName()
        if path:
            with open(path, 'r') as f:
                self.text_edit.setText(f.read())
    
    def save_file(self):
        path, _ = QFileDialog.getSaveFileName()
        if path:
            with open(path, 'w') as f:
                f.write(self.text_edit.toPlainText())

---

## 🔹 Best Practices
1. Separate UI code from business logic
2. Use models for complex data views
3. Optimize performance for large datasets
4. Localize strings for internationalization
5. Document signals and public methods

---

### 📌 What's Next?
In Part 3, we'll cover:
➡️ Dialogs & Message Boxes
➡️ File System Operations
➡️ Drag & Drop
➡️ Threading with QThread

#PyQt5 #GUIPython #ProfessionalDevelopment 🚀

Practice Exercise:
1. Create a contacts app with tree view and detail form
2. Build a styled calculator with custom buttons
3. Implement a multi-window image viewer with thumbnails

# 📚 PyQt5 Tutorial - Part 3/6: Dialogs, Files & Threading
#PyQt5 #Python #Threading #FileDialogs #DragAndDrop

Welcome to Part 3 of our PyQt5 series! This comprehensive lesson dives into professional dialog handling, file operations, drag-and-drop functionality, and threading - essential for building production-grade applications.

---

## 🔹 Professional Dialog Handling
### 1. Standard Dialogs
PyQt5 provides built-in dialogs for common tasks:

from PyQt5.QtWidgets import (QFileDialog, QColorDialog, 
                            QFontDialog, QInputDialog, QMessageBox)

# File Dialog
file_path, _ = QFileDialog.getOpenFileName(
    self, "Open File", "", "Text Files (*.txt);;All Files (*)")

# Color Dialog
color = QColorDialog.getColor()

# Font Dialog
font, ok = QFontDialog.getFont()

# Input Dialog
text, ok = QInputDialog.getText(self, "Input", "Enter your name:")

# Message Box
reply = QMessageBox.question(
    self, "Message", "Are you sure?",
    QMessageBox.Yes | QMessageBox.No, QMessageBox.No)

### 2. Custom Dialog Classes
Create reusable dialog windows:

class LoginDialog(QDialog):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle("Login")
        
        self.username = QLineEdit()
        self.password = QLineEdit()
        self.password.setEchoMode(QLineEdit.Password)
        
        buttons = QDialogButtonBox(
            QDialogButtonBox.Ok | QDialogButtonBox.Cancel)
        buttons.accepted.connect(self.accept)
        buttons.rejected.connect(self.reject)
        
        layout = QFormLayout()
        layout.addRow("Username:", self.username)
        layout.addRow("Password:", self.password)
        layout.addRow(buttons)
        
        self.setLayout(layout)
    
    def get_credentials(self):
        return (self.username.text(), self.password.text())

# Usage
dialog = LoginDialog()
if dialog.exec_():
    username, password = dialog.get_credentials()

---

## 🔹 File System Operations
### 1. File and Directory Handling

from PyQt5.QtCore import QDir, QFile, QFileInfo

# Check file existence
file_info = QFileInfo("path/to/file")
if file_info.exists():
    print("File size:", file_info.size())

# Directory operations
directory = QDir()
directory.mkdir("new_folder")
print("Current path:", directory.currentPath())

# File reading/writing
file = QFile("data.txt")
if file.open(QIODevice.ReadOnly | QIODevice.Text):
    stream = QTextStream(file)
    content = stream.readAll()
    file.close()

### 2. Monitoring File Changes

from PyQt5.QtCore import QFileSystemWatcher

class FileMonitor(QObject):
    def __init__(self):
        super().__init__()
        self.watcher = QFileSystemWatcher()
        self.watcher.fileChanged.connect(self.on_file_changed)
    
    def add_file(self, path):
        self.watcher.addPath(path)
    
    def on_file_changed(self, path):
        print(f"File changed: {path}")

monitor = FileMonitor()
monitor.add_file("important_file.txt")

---

## 🔹 Drag and Drop
### 1. Enabling Drag-and-Drop

class DropArea(QLabel):
    def __init__(self):
        super().__init__("Drop files here")
        self.setAcceptDrops(True)
        self.setAlignment(Qt.AlignCenter)
        self.setStyleSheet("border: 2px dashed #aaa;")
    
    def dragEnterEvent(self, event):
        if event.mimeData().hasUrls():
            event.acceptProposedAction()
    
    def dropEvent(self, event):
        for url in event.mimeData().urls():
            file_path = url.toLocalFile()
            print("Dropped file:", file_path)

### 2. Custom Drag Sources

class DraggableList(QListWidget):
    def __init__(self):
        super().__init__()
        self.setDragEnabled(True)
        self.setAcceptDrops(True)
        self.setDragDropMode(QAbstractItemView.InternalMove)
        
        for i in range(5):
            self.addItem(f"Item {i+1}")
    
    def startDrag(self, supportedActions):
        item = self.currentItem()
        mime_data = QMimeData()
        mime_data.setText(item.text())
        
        drag = QDrag(self)
        drag.setMimeData(mime_data)
        drag.exec_(Qt.MoveAction)

---

## 🔹 Threading with QThread
### 1. Worker Thread Pattern

class Worker(QObject):
    finished = pyqtSignal()
    progress = pyqtSignal(int)
    
    def run(self):
        for i in range(1, 101):
            time.sleep(0.1)
            self.progress.emit(i)
        self.finished.emit()

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        
        self.thread = QThread()
        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        
        self.thread.started.connect(self.worker.run)
        self.worker.finished.connect(self.thread.quit)
        self.worker.finished.connect(self.worker.deleteLater)
        self.thread.finished.connect(self.thread.deleteLater)
        self.worker.progress.connect(self.update_progress)
        
        self.thread.start()
    
    def update_progress(self, value):
        print("Progress:", value)

### 2. Thread Pool for Concurrent Tasks

from PyQt5.QtCore import QRunnable, QThreadPool

class Task(QRunnable):
    def __init__(self, task_id):
        super().__init__()
        self.task_id = task_id
    
    def run(self):
        print(f"Starting task {self.task_id}")
        time.sleep(2)
        print(f"Finished task {self.task_id}")

pool = QThreadPool.globalInstance()
for i in range(5):
    pool.start(Task(i))
print("Max threads:", pool.maxThreadCount())

---

## 🔹 Practical Example: File Processor

class FileProcessor(QMainWindow):
    def __init__(self):
        super().__init__()
        self.setup_ui()
        self.setup_thread()
    
    def setup_ui(self):
        self.setWindowTitle("File Processor")
        
        # Central Widget
        widget = QWidget()
        layout = QVBoxLayout()
        
        # File Selection
        self.file_list = QListWidget()
        self.file_list.setSelectionMode(QAbstractItemView.MultiSelection)
        
        add_btn = QPushButton("Add Files")
        add_btn.clicked.connect(self.add_files)
        
        # Processing Controls
        self.progress = QProgressBar()
        process_btn = QPushButton("Process Files")
        process_btn.clicked.connect(self.process_files)
        
        # Layout
        layout.addWidget(QLabel("Files to Process:"))
        layout.addWidget(self.file_list)
        layout.addWidget(add_btn)
        layout.addWidget(self.progress)
        layout.addWidget(process_btn)
        
        widget.setLayout(layout)
        self.setCentralWidget(widget)
    
    def setup_thread(self):
        self.thread = QThread()
        self.worker = FileWorker()
        self.worker.moveToThread(self.thread)
        
        self.thread.started.connect(self.worker.process)
        self.worker.progress.connect(self.progress.setValue)
        self.worker.finished.connect(self.on_processing_finished)
        self.worker.error.connect(self.show_error)
    
    def add_files(self):
        files, _ = QFileDialog.getOpenFileNames(
            self, "Select Files", "", "All Files (*)")
        self.file_list.addItems(files)
    
    def process_files(self):
        if self.file_list.count() == 0:
            QMessageBox.warning(self, "Warning", "No files selected!")
            return
        
        files = [self.file_list.item(i).text() 
                for i in range(self.file_list.count())]
        self.worker.set_files(files)
        self.thread.start()
    
    def on_processing_finished(self):
        self.thread.quit()
        QMessageBox.information(self, "Done", "Processing completed!")

    def show_error(self, message):
        self.thread.quit()
        QMessageBox.critical(self, "Error", message)

class FileWorker(QObject):
    progress = pyqtSignal(int)
    finished = pyqtSignal()
    error = pyqtSignal(str)
    
    def __init__(self):
        super().__init__()
        self.files = []
    
    def set_files(self, files):
        self.files = files
    
    def process(self):
        try:
            total = len(self.files)
            for i, file in enumerate(self.files):
                # Simulate processing
                time.sleep(0.5)
                
                # Check for cancellation
                if QThread.currentThread().isInterruptionRequested():
                    break
                
                # Update progress
                self.progress.emit(int((i + 1) / total * 100))
            
            self.finished.emit()
        except Exception as e:
            self.error.emit(str(e))

---

## 🔹 Best Practices
1. Always clean up threads - Use finished signals
2. Never update UI from worker threads - Use signals
3. Validate file operations - Check permissions/existence
4. Handle drag-and-drop properly - Check MIME types
5. Make dialogs modal/non-modal appropriately - exec_() vs show()

---

### 📌 What's Next?
In Part 4, we'll cover:
➡️ Database Integration (SQLite, PostgreSQL)
➡️ Data Visualization (Charts, Graphs)
➡️ Model-View-Controller Pattern
➡️ Advanced Widget Customization

#PyQt5 #ProfessionalDevelopment #PythonGUI 🚀

Practice Exercise:
1. Build a thumbnail generator with progress reporting
2. Create a JSON config editor with file monitoring
3. Implement a thread-safe logging system for background tasks

# 📚 PyQt5 Tutorial - Part 4/6: Database Integration & Data Visualization
#PyQt5 #SQL #DataViz #MVC #ProfessionalDevelopment

Welcome to Part 4 of our PyQt5 series! This comprehensive lesson covers professional database integration, data visualization, and architectural patterns for building robust desktop applications.

---

## 🔹 Database Integration with PyQt5
### 1. SQLite Connection & Setup

from PyQt5.QtSql import QSqlDatabase, QSqlQuery

def setup_database():
    db = QSqlDatabase.addDatabase("QSQLITE")
    db.setDatabaseName("app_data.db")
    
    if not db.open():
        QMessageBox.critical(None, "Database Error", db.lastError().text())
        return False
    
    # Create tables if they don't exist
    query = QSqlQuery()
    query.exec_("""
        CREATE TABLE IF NOT EXISTS contacts (
            id INTEGER PRIMARY KEY AUTOINCREMENT,
            name TEXT NOT NULL,
            email TEXT UNIQUE,
            phone TEXT,
            created_at DATETIME DEFAULT CURRENT_TIMESTAMP
        )
    """)
    return True

### 2. SQL Model-View Integration

from PyQt5.QtSql import QSqlTableModel

class ContactManager(QWidget):
    def __init__(self):
        super().__init__()
        self.model = QSqlTableModel()
        self.model.setTable("contacts")
        self.model.select()
        
        self.setup_ui()
    
    def setup_ui(self):
        layout = QVBoxLayout()
        
        # Table View
        self.table = QTableView()
        self.table.setModel(self.model)
        self.table.setSelectionBehavior(QTableView.SelectRows)
        self.table.setEditTriggers(QTableView.DoubleClicked)
        
        # Buttons
        add_btn = QPushButton("Add Contact")
        add_btn.clicked.connect(self.add_contact)
        
        del_btn = QPushButton("Delete Selected")
        del_btn.clicked.connect(self.delete_contact)
        
        # Layout
        btn_layout = QHBoxLayout()
        btn_layout.addWidget(add_btn)
        btn_layout.addWidget(del_btn)
        
        layout.addWidget(self.table)
        layout.addLayout(btn_layout)
        self.setLayout(layout)
    
    def add_contact(self):
        name, ok = QInputDialog.getText(self, "Add Contact", "Name:")
        if ok and name:
            record = self.model.record()
            record.setValue("name", name)
            self.model.insertRecord(-1, record)
            self.model.submitAll()
    
    def delete_contact(self):
        selected = self.table.selectionModel().selectedRows()
        for index in sorted(selected, reverse=True):
            self.model.removeRow(index.row())
        self.model.submitAll()

### 3. PostgreSQL Connection

def connect_postgresql():
    db = QSqlDatabase.addDatabase("QPSQL")
    db.setHostName("localhost")
    db.setDatabaseName("myapp")
    db.setUserName("postgres")
    db.setPassword("password")
    db.setPort(5432)
    
    if not db.open():
        error = db.lastError()
        QMessageBox.critical(None, "Database Error", 
                           f"Code: {error.number()}\n{error.text()}")
        return False
    return True

---

## 🔹 Data Visualization
### 1. QtCharts Basic Setup

from PyQt5.QtChart import QChart, QChartView, QBarSet, QBarSeries, QBarCategoryAxis

class SalesChart(QWidget):
    def __init__(self, data):
        super().__init__()
        self.chart = QChart()
        self.chart.setTitle("Quarterly Sales")
        self.chart.setAnimationOptions(QChart.SeriesAnimations)
        
        self.setup_series(data)
        self.setup_axes()
        
        chart_view = QChartView(self.chart)
        chart_view.setRenderHint(QPainter.Antialiasing)
        
        layout = QVBoxLayout()
        layout.addWidget(chart_view)
        self.setLayout(layout)
    
    def setup_series(self, data):
        series = QBarSeries()
        
        for product, values in data.items():
            bar_set = QBarSet(product)
            bar_set.append(values)
            series.append(bar_set)
        
        self.chart.addSeries(series)
    
    def setup_axes(self):
        categories = ["Q1", "Q2", "Q3", "Q4"]
        
        axis_x = QBarCategoryAxis()
        axis_x.append(categories)
        self.chart.addAxis(axis_x, Qt.AlignBottom)
        
        axis_y = QValueAxis()
        axis_y.setRange(0, 1000)
        self.chart.addAxis(axis_y, Qt.AlignLeft)
        
        for series in self.chart.series():
            series.attachAxis(axis_x)
            series.attachAxis(axis_y)

### 2. Interactive Line Chart

from PyQt5.QtChart import QLineSeries, QValueAxis

class InteractiveChart(QChartView):
    def __init__(self, data):
        super().__init__()
        self.series = QLineSeries()
        self.series.setName("Data Series")
        
        for point in data:
            self.series.append(*point)
        
        self.chart = QChart()
        self.chart.addSeries(self.series)
        self.chart.createDefaultAxes()
        self.chart.setTitle("Interactive Chart")
        
        self.setChart(self.chart)
        self.setRubberBand(QChartView.RectangleRubberBand)
        self.setRenderHint(QPainter.Antialiasing)
    
    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            point = self.chart.mapToValue(event.pos())
            self.series.append(point.x(), point.y())
        super().mousePressEvent(event)

### 3. Real-Time Data Visualization

class RealTimeChart(QThread):
    data_updated = pyqtSignal(list)
    
    def __init__(self):
        super().__init__()
        self.running = True
    
    def run(self):
        x = 0
        while self.running:
            time.sleep(0.1)
            y = random.randint(0, 100)
            self.data_updated.emit([(x, y)])
            x += 1
    
    def stop(self):
        self.running = False
        self.wait()

class MainWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.series = QLineSeries()
        
        self.chart = QChart()
        self.chart.addSeries(self.series)
        self.chart.createDefaultAxes()
        
        self.chart_view = QChartView(self.chart)
        self.setCentralWidget(self.chart_view)
        
        self.thread = RealTimeChart()
        self.thread.data_updated.connect(self.update_chart)
        self.thread.start()
    
    def update_chart(self, points):
        for x, y in points:
            self.series.append(x, y)
            if self.series.count() > 100:
                self.series.remove(0)
            self.chart.axisX().setRange(x-100, x)
    
    def closeEvent(self, event):
        self.thread.stop()
        super().closeEvent(event)

---

## 🔹 Model-View-Controller (MVC) Pattern
### 1. MVC Implementation

# Model
class DataModel(QObject):
    data_changed = pyqtSignal(list)
    
    def __init__(self):
        super().__init__()
        self._data = []
    
    def load_data(self, source):
        # Simulate data loading
        self._data = [(i, random.randint(0, 100)) for i in range(10)]
        self.data_changed.emit(self._data)
    
    def get_data(self):
        return self._data

# View
class DataView(QWidget):
    def __init__(self, controller):
        super().__init__()
        self.controller = controller
        self.table = QTableWidget()
        
        layout = QVBoxLayout()
        layout.addWidget(self.table)
        self.setLayout(layout)
    
    def update_view(self, data):
        self.table.setRowCount(len(data))
        self.table.setColumnCount(2)
        
        for row, (x, y) in enumerate(data):
            self.table.setItem(row, 0, QTableWidgetItem(str(x)))
            self.table.setItem(row, 1, QTableWidgetItem(str(y)))

# Controller
class DataController:
    def __init__(self):
        self.model = DataModel()
        self.view = DataView(self)
        
        self.model.data_changed.connect(self.handle_data_change)
        self.model.load_data("dummy_source")
    
    def handle_data_change(self, data):
        self.view.update_view(data)
    
    def show_view(self):
        self.view.show()

### 2. Advanced MVC with SQL

class SqlController:
    def __init__(self):
        self.db = setup_database()  # From earlier example
        self.model = QSqlTableModel()
        self.model.setTable("contacts")
        self.model.select()
        
        self.view = ContactView(self)
    
    def add_contact(self, name, email, phone):
        record = self.model.record()
        record.setValue("name", name)
        record.setValue("email", email)
        record.setValue("phone", phone)
        return self.model.insertRecord(-1, record)
    
    def delete_contact(self, row):
        return self.model.removeRow(row)

class ContactView(QWidget):
    def __init__(self, controller):
        super().__init__()
        self.controller = controller
        self.setup_ui()
    
    def setup_ui(self):
        # Form setup
        self.name_input = QLineEdit()
        self.email_input = QLineEdit()
        self.phone_input = QLineEdit()
        
        add_btn = QPushButton("Add Contact")
        add_btn.clicked.connect(self.on_add)
        
        # Table setup
        self.table = QTableView()
        self.table.setModel(self.controller.model)
        
        # Layout
        form_layout = QFormLayout()
        form_layout.addRow("Name:", self.name_input)
        form_layout.addRow("Email:", self.email_input)
        form_layout.addRow("Phone:", self.phone_input)
        form_layout.addRow(add_btn)
        
        main_layout = QVBoxLayout()
        main_layout.addLayout(form_layout)
        main_layout.addWidget(self.table)
        
        self.setLayout(main_layout)
    
    def on_add(self):
        name = self.name_input.text()
        email = self.email_input.text()
        phone = self.phone_input.text()
        
        if name:
            if self.controller.add_contact(name, email, phone):
                self.controller.model.submitAll()
                self.clear_form()
    
    def clear_form(self):
        self.name_input.clear()
        self.email_input.clear()
        self.phone_input.clear()

---

## 🔹 Advanced Widget Customization
### 1. Custom Delegate for Table Views

class ProgressBarDelegate(QStyledItemDelegate):
    def paint(self, painter, option, index):
        progress = index.data(Qt.DisplayRole)
        
        # Draw background
        painter.save()
        painter.setPen(Qt.NoPen)
        painter.setBrush(QColor("#e0e0e0"))
        painter.drawRect(option.rect)
        
        # Draw progress
        if progress > 0:
            width = option.rect.width() * progress / 100
            progress_rect = QRectF(option.rect)
            progress_rect.setWidth(width)
            
            gradient = QLinearGradient(progress_rect.topLeft(), progress_rect.topRight())
            gradient.setColorAt(0, QColor("#4CAF50"))
            gradient.setColorAt(1, QColor("#2E7D32"))
            
            painter.setBrush(QBrush(gradient))
            painter.drawRect(progress_rect)
        
        # Draw text
        painter.setPen(QColor("#333"))
        painter.drawText(option.rect, Qt.AlignCenter, f"{progress}%")
        painter.restore()

# Usage
table = QTableView()
table.setItemDelegateForColumn(2, ProgressBarDelegate())

### 2. Custom Widget with QPainter

class GaugeWidget(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.value = 0
        self.min_value = 0
        self.max_value = 100
    
    def set_value(self, value):
        self.value = max(self.min_value, min(value, self.max_value))
        self.update()
    
    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)
        
        # Draw background
        rect = self.rect().adjusted(5, 5, -5, -5)
        painter.setPen(QPen(QColor("#333"), 2)
        painter.setBrush(QColor("#f5f5f5"))
        painter.drawEllipse(rect)
        
        # Draw gauge
        angle = 180 * (self.value - self.min_value) / (self.max_value - self.min_value)
        span_angle = -angle * 16  # 1/16th of a degree
        
        pen = QPen(QColor("#FF5722"), 10)
        pen.setCapStyle(Qt.RoundCap)
        painter.setPen(pen)
        
        painter.drawArc(rect, 180 * 16, span_angle)
        
        # Draw text
        font = painter.font()
        font.setPointSize(20)
        painter.setFont(font)
        painter.drawText(rect, Qt.AlignCenter, f"{self.value}%")

---

## 🔹 Best Practices
1. Separate database logic from UI code
2. Use transactions for batch database operations
3. Optimize chart performance with limited data points
4. Follow MVC pattern for complex applications
5. Document custom widgets thoroughly

---

### 📌 What's Next?
In Part 5, we'll cover:
➡️ Networking & Web APIs
➡️ Multimedia Applications
➡️ Internationalization
➡️ Deployment & Packaging

#PyQt5 #Database #DataVisualization 🚀

Practice Exercise:
1. Build a sales dashboard with database-backed charts
2. Create a custom weather widget with API data
3. Implement an MVC-based inventory management system

# 📚 PyQt5 Tutorial - Part 5/6: Networking, Multimedia & Internationalization
#PyQt5 #Networking #Multimedia #i18n #Deployment

Welcome to Part 5 of our PyQt5 series! This comprehensive lesson covers professional networking, multimedia handling, internationalization, and deployment strategies for production applications.

---

## 🔹 Networking with PyQt5
### 1. HTTP Requests with QNetworkAccessManager

from PyQt5.QtNetwork import QNetworkRequest, QNetworkAccessManager
from PyQt5.QtCore import QUrl

class ApiClient(QObject):
    response_received = pyqtSignal(str)
    error_occurred = pyqtSignal(str)

    def __init__(self):
        super().__init__()
        self.manager = QNetworkAccessManager()
        self.manager.finished.connect(self.handle_response)

    def fetch_data(self, url):
        request = QNetworkRequest(QUrl(url))
        self.manager.get(request)

    def handle_response(self, reply):
        if reply.error():
            self.error_occurred.emit(reply.errorString())
        else:
            data = reply.readAll().data().decode('utf-8')
            self.response_received.emit(data)
        reply.deleteLater()

# Usage
client = ApiClient()
client.response_received.connect(lambda data: print("Received:", data))
client.error_occurred.connect(lambda err: print("Error:", err))
client.fetch_data("https://api.example.com/data")

### 2. WebSocket Communication

from PyQt5.QtWebSockets import QWebSocket

class WebSocketClient(QObject):
    message_received = pyqtSignal(str)
    connected = pyqtSignal()
    disconnected = pyqtSignal()

    def __init__(self):
        super().__init__()
        self.socket = QWebSocket()
        self.socket.textMessageReceived.connect(self.message_received)
        self.socket.connected.connect(self.connected)
        self.socket.disconnected.connect(self.disconnected)

    def connect_to_server(self, url):
        self.socket.open(QUrl(url))

    def send_message(self, message):
        self.socket.sendTextMessage(message)

# Usage
ws_client = WebSocketClient()
ws_client.connect_to_server("ws://echo.websocket.org")
ws_client.message_received.connect(print)

### 3. TCP Socket Server

from PyQt5.QtNetwork import QTcpServer, QTcpSocket

class TcpServer(QObject):
    new_connection = pyqtSignal(QTcpSocket)

    def __init__(self):
        super().__init__()
        self.server = QTcpServer()
        self.server.newConnection.connect(self.handle_new_connection)

    def start(self, port=12345):
        if not self.server.listen(QHostAddress.Any, port):
            print("Server error:", self.server.errorString())
            return False
        print(f"Server started on port {port}")
        return True

    def handle_new_connection(self):
        client = self.server.nextPendingConnection()
        client.readyRead.connect(lambda: self.read_data(client))
        client.disconnected.connect(client.deleteLater)
        self.new_connection.emit(client)

    def read_data(self, client):
        data = client.readAll().data().decode('utf-8')
        print("Received:", data)
        client.write(f"Echo: {data}".encode())

---

## 🔹 Multimedia Applications
### 1. Audio Player

from PyQt5.QtMultimedia import QMediaPlayer, QMediaContent
from PyQt5.QtMultimediaWidgets import QVideoWidget

class MediaPlayer(QWidget):
    def __init__(self):
        super().__init__()
        self.player = QMediaPlayer()
        self.setup_ui()

    def setup_ui(self):
        # Video display
        video_widget = QVideoWidget()
        
        # Controls
        play_btn = QPushButton("Play")
        pause_btn = QPushButton("Pause")
        stop_btn = QPushButton("Stop")
        volume_slider = QSlider(Qt.Horizontal)
        volume_slider.setRange(0, 100)
        volume_slider.setValue(50)
        
        # Layout
        control_layout = QHBoxLayout()
        control_layout.addWidget(play_btn)
        control_layout.addWidget(pause_btn)
        control_layout.addWidget(stop_btn)
        control_layout.addWidget(volume_slider)
        
        main_layout = QVBoxLayout()
        main_layout.addWidget(video_widget)
        main_layout.addLayout(control_layout)
        self.setLayout(main_layout)
        
        # Connections
        self.player.setVideoOutput(video_widget)
        play_btn.clicked.connect(self.player.play)
        pause_btn.clicked.connect(self.player.pause)
        stop_btn.clicked.connect(self.player.stop)
        volume_slider.valueChanged.connect(self.player.setVolume)
    
    def load_file(self, path):
        self.player.setMedia(QMediaContent(QUrl.fromLocalFile(path)))

### 2. Camera Capture

from PyQt5.QtMultimedia import QCamera, QCameraImageCapture
from PyQt5.QtMultimediaWidgets import QCameraViewfinder

class CameraApp(QWidget):
    def __init__(self):
        super().__init__()
        self.camera = QCamera()
        self.image_capture = QCameraImageCapture(self.camera)
        self.setup_ui()
    
    def setup_ui(self):
        # Camera viewfinder
        viewfinder = QCameraViewfinder()
        self.camera.setViewfinder(viewfinder)
        
        # Controls
        capture_btn = QPushButton("Capture")
        capture_btn.clicked.connect(self.capture_image)
        
        # Layout
        layout = QVBoxLayout()
        layout.addWidget(viewfinder)
        layout.addWidget(capture_btn)
        self.setLayout(layout)
        
        # Start camera
        self.camera.start()
    
    def capture_image(self):
        timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
        path = f"capture_{timestamp}.jpg"
        self.image_capture.capture(path)
        print(f"Image saved to {path}")

---

## 🔹 Internationalization (i18n)
### 1. Translation Setup

from PyQt5.QtCore import QTranslator, QLocale

class TranslatableApp(QApplication):
    def __init__(self, argv):
        super().__init__(argv)
        self.translator = QTranslator()
        
        # Load system language
        locale = QLocale.system().name()
        self.load_translation(locale)
    
    def load_translation(self, lang):
        # Remove old translator
        self.removeTranslator(self.translator)
        
        # Create new translator
        self.translator = QTranslator()
        if self.translator.load(f":/translations/app_{lang}.qm"):
            self.installTranslator(self.translator)
            return True
        return False

# Mark strings for translation
self.label.setText(self.tr("Welcome to the application"))

### 2. Creating Translation Files
1. Mark strings with self.tr() or QObject.tr()
2. Extract strings:

   pylupdate5 -verbose myapp.pro
   

3. Translate using Qt Linguist
4. Compile translations:

   lrelease myapp.pro

### 3. Dynamic Language Switching

class LanguageMenu(QMenu):
    language_changed = pyqtSignal(str)
    
    def __init__(self):
        super().__init__("Language")
        self.language_map = {
            "English": "en",
            "Français": "fr",
            "Español": "es",
            "中文": "zh"
        }
        
        for lang_name, lang_code in self.language_map.items():
            action = self.addAction(lang_name)
            action.triggered.connect(
                lambda _, code=lang_code: self.language_changed.emit(code))

---

## 🔹 Deployment & Packaging
### 1. PyInstaller Configuration

# Create spec file
pyi-makespec --windowed --icon=app.ico --name MyApp main.py

# Add these to the spec file:
a = Analysis(
    ['main.py'],
    datas=[
        ('translations/*.qm', 'translations'),
        ('images/*.png', 'images')
    ],
    hiddenimports=['PyQt5.QtNetwork', 'PyQt5.QtMultimedia'],
    hookspath=[],
    runtime_hooks=[],
    excludes=[],
    win_no_prefer_redirects=False,
    win_private_assemblies=False,
    cipher=block_cipher
)

### 2. Creating Installers
Windows (NSIS):

pyinstaller --onefile --windowed --icon=app.ico main.py
makensis installer.nsi

MacOS (DMG):

pyinstaller --windowed --osx-bundle-identifier com.yourcompany.yourapp main.py
hdiutil create -volname "MyApp" -srcfolder dist/MyApp.app -ov MyApp.dmg

Linux (AppImage):

pyinstaller --onefile --windowed main.py
./appimagetool-x86_64.AppImage dist/MyApp.AppDir

### 3. Updating Mechanism

class Updater(QObject):
    update_available = pyqtSignal(str)
    update_downloaded = pyqtSignal(str)
    
    def __init__(self):
        super().__init__()
        self.manager = QNetworkAccessManager()
        self.manager.finished.connect(self.handle_response)
        
    def check_for_updates(self):
        request = QNetworkRequest(QUrl("https://api.example.com/version"))
        self.manager.get(request)
    
    def handle_response(self, reply):
        if reply.error():
            print("Update check failed:", reply.errorString())
            return
            
        latest_version = reply.readAll().data().decode('utf-8')
        current_version = self.get_current_version()
        
        if latest_version > current_version:
            self.update_available.emit(latest_version)
    
    def download_update(self):
        # Implementation for downloading update package
        pass

---