这是示例代码：

#!/usr/bin/python

import gi

gi.require_version("Gtk","3.0")
gi.require_version("Gdk","3.0")

from gi.repository import Gtk,Gdk


# Main application window
# =======================
class MainWindow(Gtk.Window):
    def __init__(self):
        Gtk.Window.__init__(self)

        self.connect("delete-event",Gtk.main_quit)

        self.set_name("main-window")

        # load style from file
        cssProvider = Gtk.CssProvider()
        cssProvider.load_from_path('style.css')

        # get the default screen for the default display
        screen = Gdk.Screen.get_default()

        # new object which will store styling information affecting widget
        styleContext = Gtk.StyleContext()
        styleContext.add_provider_for_screen(screen,cssProvider,Gtk.STYLE_PROVIDER_PRIORITY_APPLICATION)

        self.resize(200,200)

        # create Box for another Boxes
        self.Box = Gtk.Box()
        self.Box.set_name("Box")
        self.add(self.Box)

        self.Box2 = Gtk.Box()
        self.Box2.set_name("Box2")
        self.Box.pack_start(self.Box2,False,0)

        self.text = Gtk.Label.new()
        self.text.set_text('text')
        self.Box2.pack_start(self.text,0)

        self.Box3 = Gtk.Box()
        self.Box3.set_name("Box3")
        self.Box.pack_start(self.Box3,0)

        self.text2 = Gtk.Label.new()
        self.text2.set_text('text2')
        self.Box3.pack_start(self.text2,0)

# Create and show window
win = MainWindow()
win.show_all()
Gtk.main()

这是CSS样式表,可以在HTML中使用

#Box {
  background: blue;
  padding: 5px;
}

#Box2 {
  background: red;
  margin: 5px;
}

#Box3 {
  background: green;
  margin: 5px;
}

但结果是：

当然我可以在python代码中添加填充/间距值,但仅适用于没有嵌套框的水平间隙.可以在没有硬编码的情况下完成,只使用css解决方案吗？