def add_item_to_sale(self):
    barcode = self.barcode_input.text()
    if not barcode:
        return
    
    drug = db.find_drug_by_barcode(barcode)
    
    if not drug:
        QMessageBox.warning(self, "Not Found", "No drug found with this barcode.")
        self.barcode_input.clear()
        return
    
    drug_id = drug[0]
    
    if drug[3] <= 0: # Check quantity
         QMessageBox.warning(self, "Out of Stock", f"{drug[1]} is out of stock.")
         self.barcode_input.clear()
         return

    if drug_id in self.current_sale_items:
        # Item already in sale, increment quantity
        self.current_sale_items[drug_id]['quantity'] += 1
    else:
        # Add new item to sale
        self.current_sale_items[drug_id] = {
            'data': drug,
            'quantity': 1
        }
    
    self.update_sales_table()
    self.barcode_input.clear()

def update_sales_table(self):
    self.sales_table.setRowCount(len(self.current_sale_items))
    total_sale_amount = 0.0
    
    for row, item in enumerate(self.current_sale_items.values()):
        drug_data = item['data']
        quantity = item['quantity']
        unit_price = drug_data[4]
        total_price = quantity * unit_price
        
        self.sales_table.setItem(row, 0, QTableWidgetItem(str(drug_data[0]))) # ID
        self.sales_table.setItem(row, 1, QTableWidgetItem(drug_data[1]))      # Name
        self.sales_table.setItem(row, 2, QTableWidgetItem(str(quantity)))
        self.sales_table.setItem(row, 3, QTableWidgetItem(f"{unit_price:.2f}"))
        self.sales_table.setItem(row, 4, QTableWidgetItem(f"{total_price:.2f}"))
        
        total_sale_amount += total_price
        
    self.total_amount_label.setText(f"{total_sale_amount:.2f}")

def complete_sale(self):
    if not self.current_sale_items:
        return

    for drug_id, item in self.current_sale_items.items():
        db.update_drug_quantity(drug_id, item['quantity'])
    
    QMessageBox.information(self, "Success", f"Sale completed. Total: {self.total_amount_label.text()}")
    
    self.clear_sale()
    self.load_inventory_data() # Refresh inventory tab to show new quantities

def clear_sale(self):
    self.current_sale_items.clear()
    self.update_sales_table()

#Hashtags: #BusinessLogic #PointOfSale #PythonCode #Transaction

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#Step 5: Results and Discussion

With all the code in place, you have a fully functional pharmacy management system.

How to Use It:
• Run the main.py script.
• Go to the "Inventory Management" tab and add a few drugs with unique barcodes.
• Go to the "Point of Sale" tab. The cursor will be in the barcode input field.
• Type a barcode of a drug you added and press Enter. The drug will appear in the sales table.
• Scan the same barcode again. The quantity for that drug in the sales table will increase to 2.
• Click "Complete Sale". A success message will appear. The sales table will clear.
• Switch back to the "Inventory Management" tab. You will see that the quantity of the sold drugs has decreased accordingly.