当您使用WASD键在屏幕上移动笔尖时，蚀刻绘图器通过描绘一条连续的线来形成一幅图片，就像蚀刻素描玩具一样。让你艺术的一面爆发出来，看看你能创造出什么形象！这个程序还可以让你把你的绘图保存到一个文本文件中，这样你以后就可以把它们打印出来。此外，你可以将其他图形的WASD运动复制粘贴到这个程序中，比如源代码第 6 到 14 行中的希尔伯特曲线分形的WASD命令。
当你运行etchingdrawer.py时，输出将看起来像图 23-1 。
:在蚀刻绘图器程序中绘制的图
与项目 17“骰子数学”一样，这个程序使用存储在名为canvas的变量中的字典来记录绘图的线条。关键字是(x, y)元组，值是表示要在屏幕上的 x，y 坐标处绘制的线形的字符串。附录 b 给出了可以在 Python 程序中使用的 Unicode 字符的完整列表。
第 126 行有一个对open()的函数调用，它传递了一个encoding='utf-8'参数。原因超出了本书的范围，但这是 Windows 将行字符写入文本文件所必需的。
"""Etching Drawer, by Al Sweigart email@protected
An art program that draws a continuous line around the screen using the
WASD keys. Inspired by Etch A Sketch toys.
For example, you can draw Hilbert Curve fractal with:
SDWDDSASDSAAWASSDSASSDWDSDWWAWDDDSASSDWDSDWWAWDWWASAAWDWAWDDSDW
Or an even larger Hilbert Curve fractal with:
DDSAASSDDWDDSDDWWAAWDDDDSDDWDDDDSAASDDSAAAAWAASSSDDWDDDDSAASDDSAAAAWA
ASAAAAWDDWWAASAAWAASSDDSAASSDDWDDDDSAASDDSAAAAWAASSDDSAASSDDWDDSDDWWA
AWDDDDDDSAASSDDWDDSDDWWAAWDDWWAASAAAAWDDWAAWDDDDSDDWDDSDDWDDDDSAASDDS
AAAAWAASSDDSAASSDDWDDSDDWWAAWDDDDDDSAASSDDWDDSDDWWAAWDDWWAASAAAAWDDWA
AWDDDDSDDWWAAWDDWWAASAAWAASSDDSAAAAWAASAAAAWDDWAAWDDDDSDDWWWAASAAAAWD
DWAAWDDDDSDDWDDDDSAASSDDWDDSDDWWAAWDD
This code is available at https://nostarch.com/big-book-small-python-programming
Tags: large, artistic"""
import shutil, sys
# Set up the constants for line characters:
UP_DOWN_CHAR = chr(9474) # Character 9474 is '│'
LEFT_RIGHT_CHAR = chr(9472) # Character 9472 is '─'
DOWN_RIGHT_CHAR = chr(9484) # Character 9484 is '┌'
DOWN_LEFT_CHAR = chr(9488) # Character 9488 is '┐'
UP_RIGHT_CHAR = chr(9492) # Character 9492 is '└'
UP_LEFT_CHAR = chr(9496) # Character 9496 is '┘'
UP_DOWN_RIGHT_CHAR = chr(9500) # Character 9500 is '├'
UP_DOWN_LEFT_CHAR = chr(9508) # Character 9508 is '┤'
DOWN_LEFT_RIGHT_CHAR = chr(9516) # Character 9516 is '┬'
UP_LEFT_RIGHT_CHAR = chr(9524) # Character 9524 is '┴'
CROSS_CHAR = chr(9532) # Character 9532 is '┼'
# A list of chr() codes is at https://inventwithpython.com/chr
# Get the size of the terminal window:
CANVAS_WIDTH, CANVAS_HEIGHT = shutil.get_terminal_size()
# We can't print to the last column on Windows without it adding a
# newline automatically, so reduce the width by one:
CANVAS_WIDTH -= 1
# Leave room at the bottom few rows for the command info lines.
CANVAS_HEIGHT -= 5
"""The keys for canvas will be (x, y) integer tuples for the coordinate,
and the value is a set of letters W, A, S, D that tell what kind of line
should be drawn."""
canvas = {}
cursorX = 0
cursorY = 0
def getCanvasString(canvasData, cx, cy):
"""Returns a multiline string of the line drawn in canvasData."""
canvasStr = ''
"""canvasData is a dictionary with (x, y) tuple keys and values that
are sets of 'W', 'A', 'S', and/or 'D' strings to show which
directions the lines are drawn at each xy point."""
for rowNum in range(CANVAS_HEIGHT):
for columnNum in range(CANVAS_WIDTH):
if columnNum == cx and rowNum == cy:
canvasStr += '#'
continue
# Add the line character for this point to canvasStr.
cell = canvasData.get((columnNum, rowNum))
if cell in (set(['W', 'S']), set(['W']), set(['S'])):
canvasStr += UP_DOWN_CHAR
elif cell in (set(['A', 'D']), set(['A']), set(['D'])):
canvasStr += LEFT_RIGHT_CHAR
elif cell == set(['S', 'D']):
canvasStr += DOWN_RIGHT_CHAR
elif cell == set(['A', 'S']):
canvasStr += DOWN_LEFT_CHAR
elif cell == set(['W', 'D']):
canvasStr += UP_RIGHT_CHAR
elif cell == set(['W', 'A']):
canvasStr += UP_LEFT_CHAR
elif cell == set(['W', 'S', 'D']):
canvasStr += UP_DOWN_RIGHT_CHAR
elif cell == set(['W', 'S', 'A']):
canvasStr += UP_DOWN_LEFT_CHAR
elif cell == set(['A', 'S', 'D']):
canvasStr += DOWN_LEFT_RIGHT_CHAR
elif cell == set(['W', 'A', 'D']):
canvasStr += UP_LEFT_RIGHT_CHAR
elif cell == set(['W', 'A', 'S', 'D']):
canvasStr += CROSS_CHAR
elif cell == None:
canvasStr += ' '
canvasStr += '\n' # Add a newline at the end of each row.
return canvasStr
moves = []
while True: # Main program loop.
# Draw the lines based on the data in canvas:
print(getCanvasString(canvas, cursorX, cursorY))
print('WASD keys to move, H for help, C to clear, '
+ 'F to save, or QUIT.')
response = input('> ').upper()
if response == 'QUIT':
print('Thanks for playing!')
sys.exit() # Quit the program.
elif response == 'H':
print('Enter W, A, S, and D characters to move the cursor and')
print('draw a line behind it as it moves. For example, ddd')
print('draws a line going right and sssdddwwwaaa draws a box.')
print()
print('You can save your drawing to a text file by entering F.')
input('Press Enter to return to the program...')
continue
elif response == 'C':
canvas = {} # Erase the canvas data.
moves.append('C') # Record this move.
elif response == 'F':
# Save the canvas string to a text file:
try:
print('Enter filename to save to:')
filename = input('> ')
# Make sure the filename ends with .txt:
if not filename.endswith('.txt'):
filename += '.txt'
with open(filename, 'w', encoding='utf-8') as file:
file.write(''.join(moves) + '\n')
file.write(getCanvasString(canvas, None, None))
except:
print('ERROR: Could not save file.')
for command in response:
if command not in ('W', 'A', 'S', 'D'):
continue # Ignore this letter and continue to the next one.
moves.append(command) # Record this move.
# The first line we add needs to form a full line:
if canvas == {}:
if command in ('W', 'S'):
# Make the first line a horizontal one:
canvas[(cursorX, cursorY)] = set(['W', 'S'])
elif command in ('A', 'D'):
# Make the first line a vertical one:
canvas[(cursorX, cursorY)] = set(['A', 'D'])
# Update x and y:
if command == 'W' and cursorY > 0:
canvas[(cursorX, cursorY)].add(command)
cursorY = cursorY - 1
elif command == 'S' and cursorY < CANVAS_HEIGHT - 1:
canvas[(cursorX, cursorY)].add(command)
cursorY = cursorY + 1
elif command == 'A' and cursorX > 0:
canvas[(cursorX, cursorY)].add(command)
cursorX = cursorX - 1
elif command == 'D' and cursorX < CANVAS_WIDTH - 1:
canvas[(cursorX, cursorY)].add(command)
cursorX = cursorX + 1
else:
# If the cursor doesn't move because it would have moved off
# the edge of the canvas, then don't change the set at
# canvas[(cursorX, cursorY)].
continue
# If there's no set for (cursorX, cursorY), add an empty set:
if (cursorX, cursorY) not in canvas:
canvas[(cursorX, cursorY)] = set()
# Add the direction string to this xy point's set:
if command == 'W':
canvas[(cursorX, cursorY)].add('S')
elif command == 'S':
canvas[(cursorX, cursorY)].add('W')
elif command == 'A':
canvas[(cursorX, cursorY)].add('D')
elif command == 'D':
canvas[(cursorX, cursorY)].add('A') 试着找出下列问题的答案。尝试对代码进行一些修改，然后重新运行程序，看看这些修改有什么影响。
- 如果把 101 行的
response = input('> ').upper()改成response = input('> ')会怎么样？ - 如果把第 61 行的
canvasStr += '#'改成canvasStr += '@'会怎么样？ - 如果把第 89 行的
canvasStr += ' '改成canvasStr += '.'会怎么样？ - 如果把 94 行的
moves = []改成moves = list('SDWDDSASDSAAWASSDSAS')会怎么样？