Creating a transparent window on top of the others

PyQt - implementation of the Qt framework for Python.

pip install PyQt5
pip install pyqt5-tools

import sys
from PyQt5.Qt import *


class Message(QDialog):      
    def __init__(self, msg: str, *args, destroy_time: int = None):
        super().__init__(*args)
        self.setWindowFlags(self.windowFlags() | 
                            Qt.FramelessWindowHint |
                            Qt.WindowStaysOnTopHint) 
        self.setAttribute(Qt.WA_TranslucentBackground)                   

        self.widget = QWidget(self)
        self.widget.setObjectName('Custom_Widget')
        layout = QVBoxLayout(self)
        layout.addWidget(self.widget)

        self.layout = QGridLayout(self.widget)
        self.layout.addItem(QSpacerItem(
            40, 20, QSizePolicy.Expanding, QSizePolicy.Minimum), 0, 0)
        self.layout.addWidget(QPushButton('r', self, 
                                          clicked=self.accept, 
                                          objectName='closeButton'), 0, 1)
        # The label
        label = QLabel(msg)
        label.setFont(QFont("Times", 14, QFont.Bold, italic=True))         
        self.layout.addWidget(label, 2, 0, 5, 2, alignment=Qt.AlignCenter)                           
        self.adjustSize()

    def mousePressEvent(self, event):
        self.old_Pos    = event.globalPos()
        self.old_width  = self.width()
        self.old_height = self.height()

    def mouseMoveEvent(self, event):
        if (event.buttons() == Qt.LeftButton): 
            delta = QPoint (event.globalPos() - self.old_Pos)
            if (self.old_Pos.x() > self.x() + self.old_width - 20) or \
               (self.old_Pos.y() > self.y() + self.old_height - 20):
                w = self.old_width+delta.x()  if self.old_width+delta.x()  > 500 else 500
                h = self.old_height+delta.y() if self.old_height+delta.y() > 400 else 400
                self.setFixedSize(w, h)
            else:
                self.move(self.x() + delta.x(), self.y() + delta.y())
                self.old_Pos = event.globalPos()


class MainWindow(QWidget):
    def __init__(self, player: QWidget):
        super().__init__()

        layout = QHBoxLayout(self)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.setSpacing(0)
        layout.addWidget(player)

        self.msg = Message("Создание прозрачного окна <br>поверх остальных - возможно.")        
        self.msg.resize(420, 420)
        self.msg.show()


Stylesheet = """
#Custom_Widget {
    background: rgba( 155, 155, 155, 150);
    border-radius: 20px;
    border: 2px solid #ff2025;  
}
#closeButton {
    min-width: 36px;
    min-height: 36px;
    font-family: "Webdings";
    qproperty-text: "r";
    border-radius: 10px;
}
#closeButton:hover {
    color: #ccc;
    background: red;
}
"""

if __name__ == '__main__':
    app = QApplication(sys.argv)
    app.setStyleSheet(Stylesheet)
    w = MainWindow(QPushButton("Button"))
    w.resize(400, 400)
    w.show()
    sys.exit(app.exec_())