The Tetris game in PyQt4
last modified October 18, 2023
In this chapter, we create a Tetris game clone.
Tetris
The Tetris game is one of the most popular computer games ever created. The original game was designed and programmed by a Russian programmer Alexey Pajitnov in 1985. Since then, Tetris is available on almost every computer platform in lots of variations.
Tetris is called a falling block puzzle game. In this game, we have seven different shapes called tetrominoes: an S-shape, a Z-shape, a T-shape, an L-shape, a Line-shape, a MirroredL-shape, and a Square-shape. Each of these shapes is formed with four squares. The shapes are falling down the board. The object of the Tetris game is to move and rotate the shapes so that they fit as much as possible. If we manage to form a row, the row is destroyed and we score. We play the Tetris game until we top out.
PyQt4 is a toolkit designed to create applications. There are other libraries which are targeted at creating computer games. Nevertheless, PyQt4 and other application toolkits can be used to create simple games.
Creating a computer game is a good way for enhancing programming skills.
The development
We do not have images for our Tetris game, we draw the tetrominoes using the drawing API available in the PyQt4 programming toolkit. Behind every computer game, there is a mathematical model. So it is in Tetris.
Some ideas behind the game:
- We use a
QtCore.QBasicTimerto create a game cycle. - The tetrominoes are drawn.
- The shapes move on a square by square basis (not pixel by pixel).
- Mathematically a board is a simple list of numbers.
The code consists of four classes: Tetris, Board, Tetrominoe
and Shape. The Tetris class sets up the game. The Board is
where the game logic is written. The Tetrominoe class contains names for all
tetris pieces and the Shape class contains the code for a tetris piece.
#!/usr/bin/python
"""
ZetCode PyQt4 tutorial
This is a Tetris game clone.
author: Jan Bodnar
website: zetcode.com
"""
import sys, random
from PyQt4 import QtCore, QtGui
class Tetris(QtGui.QMainWindow):
def __init__(self):
super(Tetris, self).__init__()
self.initUI()
def initUI(self):
self.tboard = Board(self)
self.setCentralWidget(self.tboard)
self.statusbar = self.statusBar()
self.tboard.msg2Statusbar[str].connect(self.statusbar.showMessage)
self.tboard.start()
self.resize(180, 380)
self.center()
self.setWindowTitle('Tetris')
self.show()
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):
msg2Statusbar = QtCore.pyqtSignal(str)
BoardWidth = 10
BoardHeight = 22
Speed = 300
def __init__(self, parent):
super(Board, self).__init__(parent)
self.initBoard()
def initBoard(self):
self.timer = QtCore.QBasicTimer()
self.isWaitingAfterLine = False
self.curX = 0
self.curY = 0
self.numLinesRemoved = 0
self.board = []
self.setFocusPolicy(QtCore.Qt.StrongFocus)
self.isStarted = False
self.isPaused = False
self.clearBoard()
def shapeAt(self, x, y):
return self.board[(y * Board.BoardWidth) + x]
def setShapeAt(self, x, y, shape):
self.board[(y * Board.BoardWidth) + x] = shape
def squareWidth(self):
return self.contentsRect().width() / Board.BoardWidth
def squareHeight(self):
return self.contentsRect().height() / Board.BoardHeight
def start(self):
if self.isPaused:
return
self.isStarted = True
self.isWaitingAfterLine = False
self.numLinesRemoved = 0
self.clearBoard()
self.msg2Statusbar.emit(str(self.numLinesRemoved))
self.newPiece()
self.timer.start(Board.Speed, self)
def pause(self):
if not self.isStarted:
return
self.isPaused = not self.isPaused
if self.isPaused:
self.timer.stop()
self.msg2Statusbar.emit("paused")
else:
self.timer.start(Board.Speed, self)
self.msg2Statusbar.emit(str(self.numLinesRemoved))
self.update()
def paintEvent(self, event):
painter = QtGui.QPainter(self)
rect = self.contentsRect()
boardTop = rect.bottom() - Board.BoardHeight * self.squareHeight()
for i in range(Board.BoardHeight):
for j in range(Board.BoardWidth):
shape = self.shapeAt(j, Board.BoardHeight - i - 1)
if shape != Tetrominoe.NoShape:
self.drawSquare(painter,
rect.left() + j * self.squareWidth(),
boardTop + i * self.squareHeight(), shape)
if self.curPiece.shape() != Tetrominoe.NoShape:
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.drawSquare(painter, rect.left() + x * self.squareWidth(),
boardTop + (Board.BoardHeight - y - 1) * self.squareHeight(),
self.curPiece.shape())
def keyPressEvent(self, event):
if not self.isStarted or self.curPiece.shape() == Tetrominoe.NoShape:
super(Board, self).keyPressEvent(event)
return
key = event.key()
if key == QtCore.Qt.Key_P:
self.pause()
return
if self.isPaused:
return
elif key == QtCore.Qt.Key_Left:
self.tryMove(self.curPiece, self.curX - 1, self.curY)
elif key == QtCore.Qt.Key_Right:
self.tryMove(self.curPiece, self.curX + 1, self.curY)
elif key == QtCore.Qt.Key_Down:
self.tryMove(self.curPiece.rotateRight(), self.curX, self.curY)
elif key == QtCore.Qt.Key_Up:
self.tryMove(self.curPiece.rotateLeft(), self.curX, self.curY)
elif key == QtCore.Qt.Key_Space:
self.dropDown()
elif key == QtCore.Qt.Key_D:
self.oneLineDown()
else:
super(Board, self).keyPressEvent(event)
def timerEvent(self, event):
if event.timerId() == self.timer.timerId():
if self.isWaitingAfterLine:
self.isWaitingAfterLine = False
self.newPiece()
else:
self.oneLineDown()
else:
super(Board, self).timerEvent(event)
def clearBoard(self):
for i in range(Board.BoardHeight * Board.BoardWidth):
self.board.append(Tetrominoe.NoShape)
def dropDown(self):
newY = self.curY
while newY > 0:
if not self.tryMove(self.curPiece, self.curX, newY - 1):
break
newY -= 1
self.pieceDropped()
def oneLineDown(self):
if not self.tryMove(self.curPiece, self.curX, self.curY - 1):
self.pieceDropped()
def pieceDropped(self):
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.setShapeAt(x, y, self.curPiece.shape())
self.removeFullLines()
if not self.isWaitingAfterLine:
self.newPiece()
def removeFullLines(self):
numFullLines = 0
rowsToRemove = []
for i in range(Board.BoardHeight):
n = 0
for j in range(Board.BoardWidth):
if not self.shapeAt(j, i) == Tetrominoe.NoShape:
n = n + 1
if n == 10:
rowsToRemove.append(i)
rowsToRemove.reverse()
for m in rowsToRemove:
for k in range(m, Board.BoardHeight):
for l in range(Board.BoardWidth):
self.setShapeAt(l, k, self.shapeAt(l, k + 1))
numFullLines = numFullLines + len(rowsToRemove)
if numFullLines > 0:
self.numLinesRemoved = self.numLinesRemoved + numFullLines
self.msg2Statusbar.emit(str(self.numLinesRemoved))
self.isWaitingAfterLine = True
self.curPiece.setShape(Tetrominoe.NoShape)
self.update()
def newPiece(self):
self.curPiece = Shape()
self.curPiece.setRandomShape()
self.curX = Board.BoardWidth / 2 + 1
self.curY = Board.BoardHeight - 1 + self.curPiece.minY()
#print self.curY
if not self.tryMove(self.curPiece, self.curX, self.curY):
self.curPiece.setShape(Tetrominoe.NoShape)
self.timer.stop()
self.isStarted = False
self.msg2Statusbar.emit("Game over")
def tryMove(self, newPiece, newX, newY):
for i in range(4):
x = newX + newPiece.x(i)
y = newY - newPiece.y(i)
if x < 0 or x >= Board.BoardWidth or y < 0 or y >= Board.BoardHeight:
return False
if self.shapeAt(x, y) != Tetrominoe.NoShape:
return False
self.curPiece = newPiece
self.curX = newX
self.curY = newY
self.update()
return True
def drawSquare(self, painter, x, y, shape):
colorTable = [0x000000, 0xCC6666, 0x66CC66, 0x6666CC,
0xCCCC66, 0xCC66CC, 0x66CCCC, 0xDAAA00]
color = QtGui.QColor(colorTable[shape])
painter.fillRect(x + 1, y + 1, self.squareWidth() - 2,
self.squareHeight() - 2, color)
painter.setPen(color.light())
painter.drawLine(x, y + self.squareHeight() - 1, x, y)
painter.drawLine(x, y, x + self.squareWidth() - 1, y)
painter.setPen(color.dark())
painter.drawLine(x + 1, y + self.squareHeight() - 1,
x + self.squareWidth() - 1, y + self.squareHeight() - 1)
painter.drawLine(x + self.squareWidth() - 1,
y + self.squareHeight() - 1, x + self.squareWidth() - 1, y + 1)
class Tetrominoe(object):
NoShape = 0
ZShape = 1
SShape = 2
LineShape = 3
TShape = 4
SquareShape = 5
LShape = 6
MirroredLShape = 7
class Shape(object):
coordsTable = (
((0, 0), (0, 0), (0, 0), (0, 0)),
((0, -1), (0, 0), (-1, 0), (-1, 1)),
((0, -1), (0, 0), (1, 0), (1, 1)),
((0, -1), (0, 0), (0, 1), (0, 2)),
((-1, 0), (0, 0), (1, 0), (0, 1)),
((0, 0), (1, 0), (0, 1), (1, 1)),
((-1, -1), (0, -1), (0, 0), (0, 1)),
((1, -1), (0, -1), (0, 0), (0, 1))
)
def __init__(self):
self.coords = [[0,0] for i in range(4)]
self.pieceShape = Tetrominoe.NoShape
self.setShape(Tetrominoe.NoShape)
def shape(self):
return self.pieceShape
def setShape(self, shape):
table = Shape.coordsTable[shape]
for i in range(4):
for j in range(2):
self.coords[i][j] = table[i][j]
self.pieceShape = shape
def setRandomShape(self):
self.setShape(random.randint(1, 7))
def x(self, index):
return self.coords[index][0]
def y(self, index):
return self.coords[index][1]
def setX(self, index, x):
self.coords[index][0] = x
def setY(self, index, y):
self.coords[index][1] = y
def minX(self):
m = self.coords[0][0]
for i in range(4):
m = min(m, self.coords[i][0])
return m
def maxX(self):
m = self.coords[0][0]
for i in range(4):
m = max(m, self.coords[i][0])
return m
def minY(self):
m = self.coords[0][1]
for i in range(4):
m = min(m, self.coords[i][1])
return m
def maxY(self):
m = self.coords[0][1]
for i in range(4):
m = max(m, self.coords[i][1])
return m
def rotateLeft(self):
if self.pieceShape == Tetrominoe.SquareShape:
return self
result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.setX(i, self.y(i))
result.setY(i, -self.x(i))
return result
def rotateRight(self):
if self.pieceShape == Tetrominoe.SquareShape:
return self
result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.setX(i, -self.y(i))
result.setY(i, self.x(i))
return result
def main():
app = QtGui.QApplication([])
tetris = Tetris()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
The game is simplified a bit so that it is easier to understand. The game starts immediately after it is launched. We can pause the game by pressing the p key. The Space key will drop the tetris piece instantly to the bottom. The game goes at constant speed, no acceleration is implemented. The score is the number of lines that we have removed.
self.tboard = Board(self) self.setCentralWidget(self.tboard)
An instance of the Board class is created and set to be the central
widget of the application.
self.statusbar = self.statusBar() self.tboard.msg2Statusbar[str].connect(self.statusbar.showMessage)
We create a statusbar where we display messages. We
display three possible messages: the number of lines already
removed, the paused message, or the game over message. The
msg2Statusbar is a custom signal that is implemented in
the Board class. The showMessage is a built-in method
that displays a message on a statusbar.
self.tboard.start()
This line initiates the game.
class Board(QtGui.QFrame):
msg2Statusbar = QtCore.pyqtSignal(str)
...
A custom signal is created. The msg2Statusbar is a signal
that is emitted when we want to write a message or the score to the
statusbar.
BoardWidth = 10 BoardHeight = 22 Speed = 300
These are Board's class variables. The BoardWidth and the
BoardHeight define the size of the board in blocks. The
Speed defines the speed of the game. Each 300 ms a new game
cycle will start.
... self.curX = 0 self.curY = 0 self.numLinesRemoved = 0 self.board = [] ...
In the initBoard method we initialize some important
variables.
The self.board variable is a list of numbers
from 0 to 7. It represents the position of various shapes and
remains of the shapes on the board.
def shapeAt(self, x, y):
return self.board[(y * Board.BoardWidth) + x]
The shapeAt method determines the type of a shape at
a given block.
def squareWidth(self):
return self.contentsRect().width() / Board.BoardWidth
The board can be dynamically resized. As a consequence, the size of
a block may change. The squareWidth calculates the width
of the single square in pixels and returns it. The Board.BoardWidth
is the size of the board in blocks.
for i in range(Board.BoardHeight):
for j in range(Board.BoardWidth):
shape = self.shapeAt(j, Board.BoardHeight - i - 1)
if shape != Tetrominoe.NoShape:
self.drawSquare(painter,
rect.left() + j * self.squareWidth(),
boardTop + i * self.squareHeight(), shape)
The painting of the game is divided into two steps. In the first
step, we draw all the shapes, or remains of the shapes that
have been dropped to the bottom of the board. All the squares
are remembered in the self.board list variable. The variable is accessed
using the shapeAt method.
if self.curPiece.shape() != Tetrominoe.NoShape:
for i in range(4):
x = self.curX + self.curPiece.x(i)
y = self.curY - self.curPiece.y(i)
self.drawSquare(painter, rect.left() + x * self.squareWidth(),
boardTop + (Board.BoardHeight - y - 1) * self.squareHeight(),
self.curPiece.shape())
The next step is the drawing of the actual piece that is falling down.
elif key == QtCore.Qt.Key_Right:
self.tryMove(self.curPiece, self.curX + 1, self.curY)
In the keyPressEvent method we check for pressed keys. If we press
the right arrow key, we try to move the piece to the right. We say try because
the piece might not be able to move.
elif key == QtCore.Qt.Key_Up:
self.tryMove(self.curPiece.rotateLeft(), self.curX, self.curY)
The Up arrow key will rotate the falling piece to the left.
elif key == QtCore.Qt.Key_Space:
self.dropDown()
The Space key will drop the falling piece instantly to the bottom.
elif key == QtCore.Qt.Key_D:
self.oneLineDown()
Pressing the d key, the piece will go one block down. It can be used to accellerate the falling of a piece a bit.
def tryMove(self, newPiece, newX, newY):
for i in range(4):
x = newX + newPiece.x(i)
y = newY - newPiece.y(i)
if x < 0 or x >= Board.BoardWidth or y < 0 or y >= Board.BoardHeight:
return False
if self.shapeAt(x, y) != Tetrominoe.NoShape:
return False
self.curPiece = newPiece
self.curX = newX
self.curY = newY
self.update()
return True
In the tryMove method we try to move our shapes. If the
shape is at the edge of the board or is adjacent to some
other piece, we return False. Otherwise we place the current
falling piece to a new position.
def timerEvent(self, event):
if event.timerId() == self.timer.timerId():
if self.isWaitingAfterLine:
self.isWaitingAfterLine = False
self.newPiece()
else:
self.oneLineDown()
else:
super(Board, self).timerEvent(event)
In the timer event, we either create a new piece after the previous one was dropped to the bottom or we move a falling piece one line down.
def clearBoard(self):
for i in range(Board.BoardHeight * Board.BoardWidth):
self.board.append(Tetrominoe.NoShape)
The clearBoard method clears the board by setting
Tetrominoe.NoShape at each block of the board.
def removeFullLines(self):
numFullLines = 0
rowsToRemove = []
for i in range(Board.BoardHeight):
n = 0
for j in range(Board.BoardWidth):
if not self.shapeAt(j, i) == Tetrominoe.NoShape:
n = n + 1
if n == 10:
rowsToRemove.append(i)
rowsToRemove.reverse()
for m in rowsToRemove:
for k in range(m, Board.BoardHeight):
for l in range(Board.BoardWidth):
self.setShapeAt(l, k, self.shapeAt(l, k + 1))
numFullLines = numFullLines + len(rowsToRemove)
...
If the piece hits the bottom, we call the removeFullLines method.
We find out all full lines and remove them. We do it by moving
all lines above the current full line to be removed one line down. Notice
that we reverse the order of the lines to be removed. Otherwise, it would not work correctly.
In our case we use a naive gravity. This means that the pieces
may be floating above empty gaps.
def newPiece(self):
self.curPiece = Shape()
self.curPiece.setRandomShape()
self.curX = Board.BoardWidth / 2 + 1
self.curY = Board.BoardHeight - 1 + self.curPiece.minY()
if not self.tryMove(self.curPiece, self.curX, self.curY):
self.curPiece.setShape(Tetrominoe.NoShape)
self.timer.stop()
self.isStarted = False
self.msg2Statusbar.emit("Game over")
The newPiece method creates randomly a new tetris piece.
If the piece cannot go into its initial position, the game is over.
class Tetrominoe(object):
NoShape = 0
ZShape = 1
SShape = 2
LineShape = 3
TShape = 4
SquareShape = 5
LShape = 6
MirroredLShape = 7
The Tetrominoe class holds names of all possible shapes. We have also
a NoShape for an empty space.
The Shape class saves information about a tetris piece.
class Shape(object):
coordsTable = (
((0, 0), (0, 0), (0, 0), (0, 0)),
((0, -1), (0, 0), (-1, 0), (-1, 1)),
...
)
...
The coordsTable tuple holds all possible coordinate values of our
etris pieces. This is a template from which all pieces take their
coordinate values.
self.coords = [[0,0] for i in range(4)]
Upon creation we create an empty coordinates list. The list will save the coordinates of the tetris piece.
The above image will help understand the coordinate values a bit more. For example, the tuples (0, -1), (0, 0), (-1, 0), (-1, -1) represent a Z-shape. The diagram illustrates the shape.
def rotateLeft(self):
if self.pieceShape == Tetrominoe.SquareShape:
return self
result = Shape()
result.pieceShape = self.pieceShape
for i in range(4):
result.setX(i, self.y(i))
result.setY(i, -self.x(i))
return result
The rotateLeft method rotates a piece to the left. The square does not
have to be rotated. That is why we simply return the reference to the current
object. A new piece is created and its coordinates are set to the ones of the
rotated piece.
This was a Tetris game in PyQt4.