gistfile1.py

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Window(QWidget):

    def __init__(self):
    
        QWidget.__init__(self)
	self.points = []
    
    def paintEvent(self, event):
        painter = QPainter()
        painter.begin(self)
        painter.setPen(QPen(QBrush(Qt.red), 3))

	for i in range(len(self.points) - 1):
		now = self.points[i]
		next = self.points[i + 1]

	painter.drawLine(now, next)

        painter.end()
    
    def mousePressEvent(self, event):
	self.points.append(event.pos())
    
    def mouseMoveEvent(self, event):
	self.points.append(event.pos())

        self.update()
    
    def sizeHint(self):
        return QSize(500, 500)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())