随想录（python编写的计算器和贪吃蛇游戏）

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    python除了用来开发server、web之外，一般还可以用来开发客户端，特别是用来做一些demo原型还是比较合适的。这里找了一份python编写的计算器，供大家参考一下。代码出处在这。

import Tkinter as tk

calc = tk.Tk()
calc.title("CrappyCalc")

buttons = [
'7',  '8',  '9',  '*',  'C',
'4',  '5',  '6',  '/',  'Neg',
'1',  '2',  '3',  '-',  '$',
'0',  '.',  '=',  '+',  '@' ]

# set up GUI
row = 1
col = 0
for i in buttons:
    button_style = 'raised'
    action = lambda x = i: click_event(x)
    tk.Button(calc, text = i, width = 7, height = 7, relief = button_style, command = action) \
		.grid(row = row, column = col, sticky = 'nesw', )
    col += 1
    if col > 4:
        col = 0
        row += 1

display = tk.Entry(calc, width = 40, bg = "white")
display.grid(row = 0, column = 0, columnspan = 5)

def click_event(key):

	# = -> calculate results
    if key == '=':
        # safeguard against integer division
        if '/' in display.get() and '.' not in display.get():
            display.insert(tk.END, ".0")
			
        # attempt to evaluate results
        try:
            result = eval(display.get())
            display.insert(tk.END, " = " + str(result))
        except:
            display.insert(tk.END, "   Error, use only valid chars")
			
	# C -> clear display		
    elif key == 'C':
        display.delete(0, tk.END)
		
		
	# $ -> clear display		
    elif key == '$':
        display.delete(0, tk.END)
        display.insert(tk.END, "$$$$C.$R.$E.$A.$M.$$$$")
		

	# @ -> clear display		
    elif key == '@':
        display.delete(0, tk.END)
        display.insert(tk.END, "wwwwwwwwwwwwwwwwebsite")		

		
	# neg -> negate term
    elif key == 'neg':
        if '=' in display.get():
            display.delete(0, tk.END)
        try:
            if display.get()[0] == '-':
                display.delete(0)
            else:
                display.insert(0, '-')
        except IndexError:
            pass

	# clear display and start new input		
    else:
        if '=' in display.get():
            display.delete(0, tk.END)
        display.insert(tk.END, key)

# RUNTIME
calc.mainloop()

    大家可以在此基础上做一些改写，比如如果没有eval函数，怎么用状态机来进行设计呢？

2017.1.4 补充：

    发现网上有一份python编写的贪吃蛇代码，也不错，大家可以借此多学习学习，原来地址在这。

# -*- coding:utf-8 -*-

from turtle import Vec2D
import Tkinter as tk, random, itertools

kGridWidth, kGridHeight, kGridPixels = 15, 15, 20  # 网格尺寸、网格像素数
kCanvasWidth, kCanvasHeight = kGridWidth * kGridPixels, kGridHeight * kGridPixels  # 画布尺寸
kDirs = {'Up': Vec2D(0, -1), 'Left': Vec2D(-1, 0), 'Down': Vec2D(0, 1), 'Right': Vec2D(1, 0)}  # 方向
kSceneStart, kScenePlay, kSceneOver = 0, 1, 2  # 场景
kUpdateDelay = 500  # 更新间隔（ms）

class SnakeGame:
    def __init__(self):
        self.root = tk.Tk()
        self.canvas = tk.Canvas(self.root, width=kCanvasWidth, height=kCanvasHeight, bg='gray')
        self.canvas.pack()
        self.root.bind('', self.update)
        self.valid_pos = set(map(lambda t: Vec2D(*t), itertools.product(range(kGridWidth), range(kGridHeight))))  # 有效网格坐标集合
        self.rand_pos = lambda w, h: Vec2D(random.randint(0, w - 1), random.randint(0, h - 1))  # 生成随机网格坐标
        self.food = (None, self.canvas.create_oval(0, 0, 0, 0, fill='green'))  # 食物：(网格坐标, 图形对象)
        self.snake_dir = None  # 蛇头方向：Vec2D(x, y)
        self.snake_bodys = []  # 蛇身：[(网格坐标,图形对象), ...]
        self.scene = kSceneStart  # 场景编号
        self.score = 0  # 分数
        self.update_funcs = [self.update_gamestart, self.update_gameplay, self.update_gameover]  # 场景更新函数
        self.next_update = self.root.after(kUpdateDelay, self.update)  # 延迟执行下一次更新

    def next_food(self):  # 生成下一个食物
        while True:
            pos = self.rand_pos(kGridWidth, kGridHeight)
            if pos not in map(lambda b: b[0], self.snake_bodys):  # 判定是否与蛇身冲突
                self.canvas.coords(self.food[1], (pos[0] * kGridPixels + 2, pos[1] * kGridPixels + 2,
                                                  pos[0] * kGridPixels + kGridPixels, pos[1] * kGridPixels + kGridPixels))
                self.food = (pos, self.food[1])
                return

    def move(self):  # 移动蛇头
        new_pos = self.snake_bodys[0][0] + self.snake_dir
        if new_pos not in self.valid_pos or new_pos in map(lambda b: b[0], self.snake_bodys[:-1]):  # 测试新的蛇头位置是否有效
            return False
        if new_pos == self.food[0]:  # 吃到食物时
            self.snake_bodys.insert(0, (new_pos, self.canvas.create_oval(new_pos[0] * kGridPixels + 2, new_pos[1] * kGridPixels + 2,
                                                                         new_pos[0] * kGridPixels + kGridPixels, new_pos[1] * kGridPixels + kGridPixels,
                                                                         fill='red', tags='SnakeBodys')))
            self.next_food()
            self.score += 1
        else:
            self.canvas.coords(self.snake_bodys[-1][1], (new_pos[0] * kGridPixels + 2, new_pos[1] * kGridPixels + 2,
                                                         new_pos[0] * kGridPixels + kGridPixels, new_pos[1] * kGridPixels + kGridPixels))
            self.snake_bodys.insert(0, (new_pos, self.snake_bodys.pop()[1]))  # 直接将蛇尾移动至新蛇头
        return True

    def update(self, event=None):
        self.update_funcs[self.scene](event)  # 执行当前场景的更新函数

    def update_gamestart(self, event):  # 游戏开始场景
        if event and event.keysym == 'Return':  # 按下回车
            self.canvas.delete('GameStartString')
            self.snake_dir = random.choice(kDirs.values())
            head = self.rand_pos(kGridWidth, kGridHeight)
            self.snake_bodys = [(head, self.canvas.create_oval(head[0] * kGridPixels + 2, head[1] * kGridPixels + 2,
                                                               head[0] * kGridPixels + kGridPixels, head[1] * kGridPixels + kGridPixels,
                                                               fill='red', tags='SnakeBodys'))]
            self.next_food()
            self.scene = kScenePlay
            self.next_update = self.root.after(kUpdateDelay, self.update)
        elif not self.canvas.find_withtag('GameStartString'):  # 画面初始化
            self.canvas.create_text((kCanvasWidth / 2, kCanvasHeight / 6 * 2), text='Welcome to the simple snake game.', tags='GameStartString')
            self.canvas.create_text((kCanvasWidth / 2, kCanvasHeight / 6 * 3), text='Move the snake with .', tags='GameStartString')
            self.canvas.create_text((kCanvasWidth / 2, kCanvasHeight / 6 * 4), text='Please press  to start.', tags='GameStartString')

    def update_gameplay(self, event):  # 游戏进行场景
        try:
            if event and event.keysym in kDirs and kDirs[event.keysym] + self.snake_dir != Vec2D(0, 0):  # 按下方向键且与当前方向不相反时
                self.root.after_cancel(self.next_update)
                self.snake_dir = kDirs[event.keysym]
                if not self.move():
                    raise  # 懒
            elif not event:  # 自动更新时
                if not self.move():
                    raise
            else:  # 忽略其他按键
                return
        except:  # 死亡
            self.canvas.delete('SnakeBodys')
            self.canvas.coords(self.food[1], (0, 0, 0, 0))
            self.scene = kSceneOver
        self.next_update = self.root.after(kUpdateDelay, self.update)  # 延迟执行下一次更新

    def update_gameover(self, event):  # 游戏结束场景
        if event and event.keysym == 'Escape':  # 按下Esc
            self.canvas.delete('GameOverString')
            self.scene = kSceneStart
            self.next_update = self.root.after(kUpdateDelay, self.update)
        elif not self.canvas.find_withtag('GameOverString'):  # 画面初始化
            self.canvas.create_text((kCanvasWidth / 2, kCanvasHeight / 5 * 2), text='Your score is: %d' % self.score, tags='GameOverString')
            self.canvas.create_text((kCanvasWidth / 2, kCanvasHeight / 5 * 3), text='Please press  to restart.', tags='GameOverString')

if __name__ == '__main__':
    SnakeGame().root.mainloop()