Decide two items on top of each other,is there a z-index?

I am using pyqt4 and I have drawn a line and a rectangle on.Now since they are on the same coordinate they overlap. I wanted to know if there is a z-index(used in css) sort of a thing which I can use to show or hide either the line on top of the triangle or vice versa.Also adding the code by how I have a line and rectangle.

Code:

from PyQt4 import QtGui
from PyQt4 import QtCore
import pyqtgraph as pg
import webcolors
 
 
class LineSegmentItem(pg.GraphicsObject):
    def __init__(self, p1, p2,color):
        pg.GraphicsObject.__init__(self)
        self.p1 = p1
        self.p2 = p2
        self.color=color
        self.generatePicture()
 
    def generatePicture(self):
        self.picture = QtGui.QPicture()
        self.p = QtGui.QPainter(self.picture)
        self.p.setPen(pg.mkPen(self.color))
        self.p.drawLine(QtCore.QPoint(self.p1[0], self.p1[1]), QtCore.QPoint(self.p2[0], self.p2[1]))
        self.p.end()
 
    def paint(self, p, *args):
        p.drawPicture(0, 0, self.picture)
 
    def boundingRect(self):
        return QtCore.QRectF(self.picture.boundingRect())
 
    def modifyColor(self,color):
        self.color=color
        self.generatePicture()
 
    def stretchLine(self,toSecondCoordinate):
        self.p2[0]=toSecondCoordinate
        self.update()
 
    def getToSecondCoordinate(self):
        return self.p2[0]
 
 
class CircleItem(pg.GraphicsObject):
    def __init__(self, center, radius):
        pg.GraphicsObject.__init__(self)
        self.center = center
        self.radius = radius
        self.generatePicture()
 
    def generatePicture(self):
        self.picture = QtGui.QPicture()
        p = QtGui.QPainter(self.picture)
        p.setPen(pg.mkPen('w'))
        p.drawEllipse(self.center[0], self.center[1], self.radius * 2, self.radius * 2)
        p.end()
 
    def paint(self, p, *args):
        p.drawPicture(0, 0, self.picture)
 
    def boundingRect(self):
        return QtCore.QRectF(self.picture.boundingRect())
 
 
class RectangleItem(pg.GraphicsObject):
    def __init__(self, p1,p2,color,tickSize):
        pg.GraphicsObject.__init__(self)
        self.topLeft = p1
        self.size = [abs(p2[0]-p1[0]),tickSize]
        self.color=color
        self.generatePicture()
 
    def generatePicture(self):
        self.picture = QtGui.QPicture()
        p = QtGui.QPainter(self.picture)
        p.setPen(pg.mkPen(self.color))
 
        r,g,b=self.color
        p.setBrush(QtGui.QColor(r,g,b))
        tl = QtCore.QPointF(self.topLeft[0], self.topLeft[1])
        size = QtCore.QSizeF(self.size[0], self.size[1])
        p.drawRect(QtCore.QRectF(tl, size))
        p.end()
 
    def paint(self, p, *args):
        p.drawPicture(0, 0, self.picture)
 
    def boundingRect(self):
        return QtCore.QRectF(self.picture.boundingRect())
 
    def modifyColor(self,color):
        self.color=color
        self.generatePicture()
 
    def stretchLine(self,toSecondCoordinate):
        self.size[0]=toSecondCoordinate-self.topLeft[0]
        self.update()
 
    def getToSecondCoordinate(self):
        return self.size[0]

Attachment 12391