我想用python编写一个俄罗斯方块的问题

我准备用python编写一个俄罗斯方块，网上代码已经有了，但是没有代码的讲解，有人能帮我讲解下这每行代码是什么意思吗？求大神谢谢了啊，分还会加大！！
由于字数有限，先讲讲前面几行代码是什么意思也行的啊

import sys
import random
from PyQt4 import QtCore, QtGui
class Tetris(QtGui.QMainWindow):
def __init__(self):
QtGui.QMainWindow.__init__(self)
self.setGeometry(300, 300, 180, 380)
self.setWindowTitle('Tetris')
self.tetrisboard = Board(self)
self.setCentralWidget(self.tetrisboard)
self.statusbar = self.statusBar()
self.connect(self.tetrisboard, QtCore.SIGNAL("messageToStatusbar(QString)"),
self.statusbar, QtCore.SLOT("showMessage(QString)"))
self.tetrisboard.start()
self.center()
def center(self):
screen = QtGui.QDesktopWidget().screenGeometry()
size = self.geometry()
self.move((screen.width()-size.width())/2,
(screen.height()-size.height())/2)
class Board(QtGui.QFrame):
BoardWidth = 10
BoardHeight = 22
Speed = 300
def __init__(self, parent):
QtGui.QFrame.__init__(self, parent)
self.timer = QtCore.QBasicTimer()
self.isWaitingAfterLine = False
self.curPiece = Shape()
self.nextPiece = Shape()
self.curX = 0
self.curY = 0
self.numLinesRemoved = 0
self.board = []
self.setFocusPolicy(QtCore.Qt.StrongFocus)
self.isStarted = False
self.isPaused = False
self.clearBoard()
self.nextPiece.setRandomShape()

这是用PyQT写的，建议看一下QT的signal slot机制，几句话说不清楚。你可以理解为当信号触发时，会调用connect到对象的SIGNAL的slot函数。这里在随后的代码中emit了自定义的messageToStatusbar(QString)信号。 网上有解释：www. czug. org/python/pyqt4/11.htm

期待看到有用的回答！