Hey there! Let's break down your problems one by one and fix them properly—starting with the most annoying one: losing your custom code every time you regenerate the UI file.

The golden rule here is never modify the auto-generated .py file from pyuic5. Those files are meant to be read-only artifacts. Instead, use a separate wrapper file to implement your custom widgets and logic, leaving the UI-generated file untouched. Here's a clean project structure to follow:

your_project/
├── tab.ui          # Edit this in Qt Designer (source file)
├── tab_ui.py       # Auto-generated by pyuic5 (don't edit!)
└── custom_tab_window.py  # Your custom code lives here

Step-by-step implementation: #

1. Regenerate your UI file with a clear name (to avoid confusion):

   pyuic5 tab.ui -o tab_ui.py
   

2. Create custom_tab_window.py with this code (adjust class names to match your UI):

   from PyQt5.QtWidgets import (QTabWidget, QTabBar, QProxyStyle, 
                                QWidget, QApplication, QVBoxLayout)
   from tab_ui import Ui_Form  # Import the auto-generated UI class
   
   # Your custom TabBar (keep all your existing logic here)
   class CustomTabBar(QTabBar):
       def __init__(self, parent=None):
           super().__init__(parent)
           # Add your custom tab bar logic (e.g., custom painting, size hints)
   
   # Your custom TabWidget
   class CustomTabWidget(QTabWidget):
       def __init__(self, parent=None):
           super().__init__(parent)
           self.setTabBar(CustomTabBar(self))
   
   # Your custom ProxyStyle
   class CustomProxyStyle(QProxyStyle):
       def pixelMetric(self, metric, option=None, widget=None):
           # Override metrics to tweak padding/margins
           if metric == QProxyStyle.PM_TabBarTabContentPadding:
               return 10  # Adjust this value to fix inner tab padding
           return super().pixelMetric(metric, option, widget)
   
   # Main window wrapper that combines UI and custom logic
   class MainWindow(QWidget):
       def __init__(self):
           super().__init__()
           self.ui = Ui_Form()
           self.ui.setupUi(self)
           
           # Replace default QTabWidget with your custom one
           old_tab = self.ui.tabWidget
           self.ui.verticalLayout.removeWidget(old_tab)
           old_tab.deleteLater()
           
           self.custom_tab = CustomTabWidget()
           self.ui.verticalLayout.addWidget(self.custom_tab)
           
           # Reattach your original tab pages (match names from tab_ui.py)
           self.custom_tab.addTab(self.ui.tab_account, "Account")
           self.custom_tab.addTab(self.ui.tab_security, "Security")
           self.custom_tab.addTab(self.ui.tab_performance, "Performance")
           
           # Apply your proxy style
           self.custom_tab.setStyle(CustomProxyStyle())
           
           # Ensure proper resizing
           self.setWindowTitle("Custom Tab Manager")
   
   if __name__ == "__main__":
       import sys
       app = QApplication(sys.argv)
       window = MainWindow()
       window.show()
       sys.exit(app.exec_())
   

Now, every time you update tab.ui and regenerate tab_ui.py, your custom code stays safe.

This is almost always caused by missing layout managers in your tab.ui file. Fix it in Qt Designer:

• For each tab page (Account/Security/Performance):
  1. Select the inner widget that holds your tab content
  2. Go to the Layout menu and apply a layout (e.g., Vertical Layout or Grid Layout)
  3. In the Property Editor (bottom-right), set the layout's Contents Margins and ensure sizePolicy for child widgets is set to Expanding
• For the main window:
  1. Make sure the top-level widget has a layout that contains the tab widget (no fixed sizes allowed!)
  2. Test resizing with the Preview button (Ctrl+R) before saving the UI.

You have two flexible ways to adjust padding:

Option 1: Tweak via ProxyStyle #

Expand your CustomProxyStyle to adjust more metrics:

class CustomProxyStyle(QProxyStyle):
    def pixelMetric(self, metric, option=None, widget=None):
        if metric == QProxyStyle.PM_TabBarTabContentPadding:
            return 8  # Smaller = tighter padding; larger = more space
        elif metric == QProxyStyle.PM_TabBarTabMargin:
            return 4  # Space between individual tabs
        return super().pixelMetric(metric, option, widget)

Option 2: Use Qt Style Sheets #

Add this to your MainWindow __init__ for fine-grained control:

self.custom_tab.setStyleSheet("""
    QTabBar::tab {
        padding: 8px 16px;  /* Top/bottom | left/right padding for tab buttons */
        margin: 2px;        /* Gap between tabs */
    }
    QTabWidget::pane {
        border: 1px solid #ccc;
        padding: 12px;      /* Padding inside the tab content area */
    }
""")

内容的提问来源于stack exchange，提问作者Dhurjati Riyan