# 📚 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.

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## 🔹 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")

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## 🔹 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)