我们将会用一些简单的远古电脑小游戏作为 Python 入门的练习. 这些小游戏来自 Computer Battle Games (For ZX Spectrum, ZX81, TRS-80, APPLE, VIC & PET), 是一本由 Usborne 出版社, 出版于 1982 年的适用于儿童的计算机普及读物.
你可以在 Intenet Archive 网站上游览或者下载它, 或者你也可以在 Usborne 的存档网站上找到同一系列的书籍. 不过本部分并不会完全按照原书的内容进行介绍 (毕竟原书是 BASIC 语言, 而非 Python). 不过你可以将其作为课外消遣读物, 不过毕竟是儿童计算机读物, 对小学生来说可能有些幼稚, 但是对大学生来说估计刚刚好.
你应该对 Python 有稍微的了解, 这里推荐阅读 这篇文章中的 Pythonin 20 min 一节, 小小花个 20 分钟入个门.
为了方便, 对于原文中比较中二的背景设定我直接使用的是 OCR 识别, 所以如果有 typo, 请提交 issue 来修改.
The year is 2582 and the people of Earth are in the midst of battle against the Robots. A lethal Robot Missile has just landed and everyone is depending on you to find the secret code which unlocks its defuse mechanism. If you fail, the entire Earth Command Headquarters will be blown up.
Your computer knows what the code letter is. You must type in your guess and it will tell you whether the code letter is earlier or later in the alphabet.
You have four chances to find the correct letter before the missile blows up.
请参考 robot-missile.py.
我们发现这个小游戏完全可以用二分法 来解决,
因为 math.log(26) = 3.25 < 4.
那么我们完全可以写一个简单的二分搜索小外挂:
def guess_number():
# 这里用到了一个多赋值
left, right = 'A', 'Z'
# 这里 // 是整除
guess = chr((ord(left) + ord(right)) // 2)
while True:
if success_p(guess):
return guess
elif later_p(guess):
left, right = guess, right
guess = chr((ord(left) + ord(right)) // 2)
else:
left, right = left, right
guess = chr((ord(left) + ord(right)) // 2)
if left == right:
return None
我们在课上将会介绍如何编写 success_p 以及 later_p 的函数,
来和外部的程序进行 IO 交互并且自动化输入命令. (这是一个查文档的例子)
You are a laser communications operator. Your job is to intercept robot messages and relay them to Command HQ. A vital code message is expected. If you relay it correctly, the Robot attack will be crushed.
This game tests your skill at remembering a group of letters which you see for only a very short time. The computer will ask you for a difficulty from 4 to 10. When you have typed in your answer, letters will appear top left of your screen and disappear again fairly quickly. Memorize them and then type them into the computer and see if you were right.
请参考 vital-message.py.
这个游戏其实原理非常简单, 所以我们并不会对这个游戏的逻辑进行解释. 在这里我们将会换一些考查视角: 如果用户不按照我们想要的方式输入, 那么会发送什么? 如果用户的设备不是 Unix-like, 那么代码会发生什么?
即, 如何处理用户输入以及如何处理多端移植.
You are standing back to back. You take 10 paces, turn and reach for your gun. How quick are you? Can you shoot first?
Your computer prints the numbers 1 to 10 to represent the 10 paces, pauses and then prints HE DRAWS…
You must be ready to press a key (any one will do) the instant these words come of the screen. If you are quick enough, you will win. Don’t press a key before HE DRAWS comes up or you automatically lose.
(coming soon… or we could write it on class)
The last major stronghold of Robot forces outside the U.R.S* is hidden in ancient castle ruins in the middle of the desert. A fleet of desert hovertanks has beensent to destroy it and you are the commander. Your tank controls the five remaining missiles.
You must assess carefully the direction and elevation before you launch each one. Your computer will ask you for a direction angle between -90° (extremeleft) and +90° (extreme right) and an elevation angle between 0° (along the ground) and 90° (straight up in the air). The elevation determines the distance the missile will travel.
Is your aim good enough to destroy the robot stronghold?
老实说, 这几个代码其实都是差不多的原理, 看那么多类似的代码其实更多的是提高熟练度.
但是这是为了作为课程练习, 所以我们需要一些新的东西来不让我们像是在原地踏步. 所以在这个例子中, 我们做的事情是一个代码的 “转写” 工作. 我们会拿到一个 BASIC 代码 (其实不管是什么代码都行), 然后我们需要将其变成一个 Python 代码.
10 PRINT "DESERT TANK BATTLE"
20 LET T=INT(RND*181)-90
30 LET D=RND
40 FOR G=1 TO 5
50 PRINT "DIRECTION (-90 TO 90) ?"
60 INPUT T1
70 PRINT "ELEVATION (0 TO 90) ?"
80 INPUT B
90 LET D1=SIN(2*(B/180*3.1416))
100 IF ABS(T-T1)<2 AND ABS(D-D1)<.05 THEN GOTO 220
110 PRINT "MISSILE LANDED ";
120 IF T1<T THEN PRINT "TO THE LEFT ";
130 IF T1>T THEN PRINT "TO THE RIGHT ";
140 IF ABS(D1-D)>.05 AND T1<>T THEN PRINT "AND ";
150 IF D-D1>.05 THEN PRINT "NOT FAR ENOUGH";
160 IF D1-D>.05 THEN PRINT "TOO FAR";
170 PRINT
180 NEXT G
190 PRINT "DISASTER - YOU FAILED:
200 PRINT "RETREAT IN DISGRACE"
210 STOP
220 PRINT "*KABOOOMMM*"
230 PRINT "YOU'VE DONE IT"
240 STOP
评价: 其实完全和前面的 Robot Missile 是差不多的逻辑, 所以你也可以尝试用 Robot Missile 中写外挂的技术来进行一个外挂的编.
这是一个简单的转写例子, 你可能需要随时查询 BASIC 的用法, 以及搞到一台能跑 BASIC 的模拟器.
这里推荐使用 APPLE II 的 BASIC (applesoft 链接, 或是 jsbasic).
当然, 有兴趣的同学可以尝试编写一个 BASIC 的解释器, 如果将来有时间, 我们可以考虑用这个 BASIC 来作为一个简单虚拟机的练习.
Your hull is badly damaged and you’ve no weapons to speak of. As you limp slowly home through treacherous iceberg-strewn waters, you become aware that an enemy ship is tailing you. Strangely it can detect you but not the icebergs, so your best chance is to lure it into hitting one.
Your computer will print a grid showing the position of your ship (🚢), the enemy (😈) and the icebergs (🏔️). You can move one space North, South, East or West each go. The enemy moves towards you by the most direct route (it can move diagonally too). If you move into any of the 8 positions surrounding the enemy, you will be captured, and if you hit an iceberg you will sink.
Can you escape?
是时候该从这些过于朴实无华的终端文本界面升级一下了,
我们将会演示如何下载并调用一个 TUI 的图形库: curses.
我们最终的目标是做一个能够显示如下效果的小游戏:
这里默认大家使用的是 Windows 作为自己的编程环境, 假如是 Unix-like 的环境, 那么大家可以只是看看这里的操作而不必真的执行下面的命令:
pip 命令:pip install windows-curses
这里, 我们使用 pip install 命令来下载一个叫作 windows-curses 的库.
类似的, 你完全可以下载其他任何的库, 比如 numpy, scipy 等等.
curses 库呢?首先, 相信大家的第一个想法就是跑到万能的互联网上搜索 curses 教程
关键词来找到或是 CSDN 或是 b 站视频或是别的什么的网站来找一个教程.
但是, 其实还有一个非常好用的文档/教程来源: 那就是官方的文档: curses. 让我们来看看下面的这段代码:
# from https://docs.python.org/3/howto/curses.html#starting-and-ending-a-curses-application
from curses import wrapper
def main(stdscr):
# Clear screen
stdscr.clear()
# This raises ZeroDivisionError when i == 10.
for i in range(0, 11):
v = i-10
stdscr.addstr(i, 0, '10 divided by {} is {}'.format(v, 10/v))
stdscr.refresh()
stdscr.getkey()
wrapper(main)
将这段代码保存到一个 Python 文件中: curses-example.py,
然后在终端中运行 python curses-exaple.py.
因为大部分的 IDE 的终端是终端模拟器而非完整的终端, 而 curses 的背后其实是 C 的 curses 库, 需要一个终端环境.
那么请参考代码: iceberg.py.
其实代码写完了并不意味着这个程序就没有继续升级的地方了. 我们可以添加许多有意思的功能, 或者对代码进行重构和优化, 以提升可读性或是性能.
在这里我们将会以 Iceberg 的代码为例进行一定的优化和一般化. 假如还有时间的话, 我们可以介绍一下该如何用 OOP 的方式, 来重新构造这个小游戏的代码.