from PyQt5.QtWidgets import QApplication, QMainWindow, QLabel
from PyQt5.QtGui import QPixmap, QPainter, QColor, QPen
from PyQt5.QtCore import Qt
from random import randint, choice


class MainWindow(QMainWindow):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.label = QLabel()
        canvas = QPixmap(400, 300)
        canvas.fill(Qt.white)
        self.label.setPixmap(canvas)

        self.setCentralWidget(self.label)
        self.draw_something()

    def draw_something(self):
        colors = [
            "#ffd141",
            "#376f9f",
            "#0d1f2d",
            "#e9ebef",
            "#eb5160",
        ]
        painter = QPainter(self.label.pixmap())
        pen = QPen()
        pen.setWidth(3)
        pen.setColor(QColor("red"))
        painter.setPen(pen)

        for n in range(10000):
            pen.setColor(QColor(choice(colors)))
            painter.setPen(pen)
            painter.drawPoint(
                200 + randint(-100, 100),
                150 + randint(-100, 100),
            )
        painter.end()


if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = MainWindow()
    window.show()
    sys.exit(app.exec_())