The following code creates a range slider as a Qt widget with a native looks and feel

RangeSlider.py

from PySide2.QtWidgets import *
from PySide2.QtCore import *
from PySide2.QtGui import *

import sys


class RangeSlider(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.first_position = 1
        self.second_position = 8

        self.opt = QStyleOptionSlider()
        self.opt.minimum = 0
        self.opt.maximum = 10

        self.setTickPosition(QSlider.TicksAbove)
        self.setTickInterval(1)

        self.setSizePolicy(
            QSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed, QSizePolicy.Slider)
        )

    def setRangeLimit(self, minimum: int, maximum: int):
        self.opt.minimum = minimum
        self.opt.maximum = maximum

    def setRange(self, start: int, end: int):
        self.first_position = start
        self.second_position = end

    def getRange(self):
        return (self.first_position, self.second_position)

    def setTickPosition(self, position: QSlider.TickPosition):
        self.opt.tickPosition = position

    def setTickInterval(self, ti: int):
        self.opt.tickInterval = ti

    def paintEvent(self, event: QPaintEvent):

        painter = QPainter(self)

        # Draw rule
        self.opt.initFrom(self)
        self.opt.rect = self.rect()
        self.opt.sliderPosition = 0
        self.opt.subControls = QStyle.SC_SliderGroove | QStyle.SC_SliderTickmarks

        #   Draw GROOVE
        self.style().drawComplexControl(QStyle.CC_Slider, self.opt, painter)

        #  Draw INTERVAL

        color = self.palette().color(QPalette.Highlight)
        color.setAlpha(160)
        painter.setBrush(QBrush(color))
        painter.setPen(Qt.NoPen)

        self.opt.sliderPosition = self.first_position
        x_left_handle = (
            self.style()
            .subControlRect(QStyle.CC_Slider, self.opt, QStyle.SC_SliderHandle)
            .right()
        )

        self.opt.sliderPosition = self.second_position
        x_right_handle = (
            self.style()
            .subControlRect(QStyle.CC_Slider, self.opt, QStyle.SC_SliderHandle)
            .left()
        )

        groove_rect = self.style().subControlRect(
            QStyle.CC_Slider, self.opt, QStyle.SC_SliderGroove
        )

        selection = QRect(
            x_left_handle,
            groove_rect.y(),
            x_right_handle - x_left_handle,
            groove_rect.height(),
        ).adjusted(-1, 1, 1, -1)

        painter.drawRect(selection)

        # Draw first handle

        self.opt.subControls = QStyle.SC_SliderHandle
        self.opt.sliderPosition = self.first_position
        self.style().drawComplexControl(QStyle.CC_Slider, self.opt, painter)

        # Draw second handle
        self.opt.sliderPosition = self.second_position
        self.style().drawComplexControl(QStyle.CC_Slider, self.opt, painter)

    def mousePressEvent(self, event: QMouseEvent):

        self.opt.sliderPosition = self.first_position
        self._first_sc = self.style().hitTestComplexControl(
            QStyle.CC_Slider, self.opt, event.pos(), self
        )

        self.opt.sliderPosition = self.second_position
        self._second_sc = self.style().hitTestComplexControl(
            QStyle.CC_Slider, self.opt, event.pos(), self
        )

    def mouseMoveEvent(self, event: QMouseEvent):

        distance = self.opt.maximum - self.opt.minimum

        pos = self.style().sliderValueFromPosition(
            0, distance, event.pos().x(), self.rect().width()
        )

        if self._first_sc == QStyle.SC_SliderHandle:
            if pos <= self.second_position:
                self.first_position = pos
                self.update()
                return

        if self._second_sc == QStyle.SC_SliderHandle:
            if pos >= self.first_position:
                self.second_position = pos
                self.update()

    def sizeHint(self):
        """ override """
        SliderLength = 84
        TickSpace = 5

        w = SliderLength
        h = self.style().pixelMetric(QStyle.PM_SliderThickness, self.opt, self)

        if (
            self.opt.tickPosition & QSlider.TicksAbove
            or self.opt.tickPosition & QSlider.TicksBelow
        ):
            h += TickSpace

        return (
            self.style()
            .sizeFromContents(QStyle.CT_Slider, self.opt, QSize(w, h), self)
            .expandedTo(QApplication.globalStrut())
        )


if __name__ == "__main__":

    app = QApplication(sys.argv)

    w = RangeSlider()
    w.show()

    # q = QSlider()
    # q.show()

    app.exec_()

Thank you for this amazing tool : ) I really enjoy using it! I noticed, that if you set a positive value for opt.minimum the right slider won't be able to get to the maximum value anymore. It seems that the distance in the mouseMoveEvent is not necessary. To fix this 'bug' I just used:

pos = self.style().sliderValueFromPosition(
    self.opt.minimum, self.opt.maximum, event.pos().x(), self.rect().width()
) 

Hi ! Thanks !
You can suggest an update of the full code here .

Does it support stylesheets?