如何使用Python在列表中填写海龟方向？

Question

我有一张海龟方向的清单：

redlist = ['seth(0)', 'forward(drawdist)', 'seth(0)', 'forward(drawdist)', 'seth(90)', 'forward(drawdist)', 'seth(90)', 'forward(drawdist)', 'seth(180)', 'forward(drawdist)', 'seth(180)', 'forward(drawdist)', 'seth(270)', 'forward(drawdist)', 'seth(270)', 'forward(drawdist)']

我如何使用列表填写此表？

Answer 1

尽管像这样一系列语法正确的Python语句看起来是使用eval()的好机会，但还是要抵制住这种诱惑。这里的语法非常简单，只有一个参数的函数，我们可以使用re模块来解析命令，并且只对有效参数执行看起来有效的函数：

import turtle
import re

redist = [ \
    'seth(0)', 'forward(drawdist)', 'seth(0)', 'forward(drawdist)', \
    'seth(90)', 'forward(drawdist)', 'seth(90)', 'forward(drawdist)', \
    'seth(180)', 'forward(drawdist)', 'seth(180)', 'forward(drawdist)', \
    'seth(270)', 'forward(drawdist)', 'seth(270)', 'forward(drawdist)' \
    ]

valid_functions = { \
    'seth': turtle.setheading, \
    'forward': turtle.forward, \
    }

valid_arguments = { \
    'drawdist': 50, \
    }

turtle.begin_fill()

for command in redist:
    match = re.match(r"^(\w+)\((\w+)\)$", command)

    if match is None:
        raise SyntaxError("Invalid syntax")

    function, argument = match.group(1), match.group(2)

    if function not in valid_functions:
        raise ValueError("Invalid function")

    if argument in valid_arguments:
        argument = valid_arguments[argument]
    elif argument.isdigit():
        argument = int(argument)
    else:
        raise TypeError("Invalid argument")

    valid_functions[function](argument)

turtle.end_fill()

turtle.hideturtle()

turtle.mainloop()

对于那些想要提前阅读的人来说，它会绘制一个实心的方块。我在上面提出的异常可能不是正确的，但重点是，当试图执行作为字符串传递给您的代码时，您需要对所有内容进行错误检查，并引发异常。

Answer 2

在循环中使用pendown，然后使用fillcolor方法：

def draw_n_fill(self,redlist):
  self.pendown()
  [self.getAttr(entry)() for entry in redlist] 
  self.fillcolor("red")

参考

• How to draw a ring of colors using turtle module in python
• Python: Using Turtles for Drawing Circles
• Summary of Turtle Methods