from gi.repository import Gtk


widget = Gtk.Box()
print(dir(widget.props))

['app_paintable', 'baseline_position', 'border_width', 'can_default', 'can_focus', 'child', 'composite_child', 'double_buffered', 'events', 'expand', 'halign', 'has_default', 'has_focus', 'has_tooltip', 'height_request', 'hexpand', 'hexpand_set', 'homogeneous', 'is_focus', 'margin', 'margin_bottom', 'margin_end', 'margin_left', 'margin_right', 'margin_start', 'margin_top', 'name', 'no_show_all', 'opacity', 'orientation', 'parent', 'receives_default', 'resize_mode', 'scale_factor', 'sensitive', 'spacing', 'style', 'tooltip_markup', 'tooltip_text', 'valign', 'vexpand', 'vexpand_set', 'visible', 'width_request', 'window']