带有海龟图形的 Python 中的字符 S、5 和 3？

Question

Currently I am trying to use commands to tell a turtle to draw the characters "S," "3," and "5" using the turtle module - without using the command turtle.write. Currently my code looks like:

import turtle

def halfcircle(parts=360, line=1, direction=1):
    for x in range(parts//2):
        turtle.forward(line)
        turtle.left(360/parts * direction)

turtle.tracer(False)

for x in range(2):
    halfcircle(20, 360/30, 1)
    halfcircle(20, 360/30, -1)

turtle.update() 

But the loop is never ending. Additionally, I am unable to incorporate linear and nonlinear lines into one character in order to draw a 5 or 3. Any help would be much appreciated.

Answer 1

Before I could actually check this out, I had to add an extra line of turtle.exitonclick() to the script to prevent it from disappearing from my screen as soon as I ran it.

From what I'm seeing, it doesn't appear to actually be never ending. The turtle draws four half-circle shapes then stops. When you say never ending, do you mean that it's repeating more than you wanted/expected? Or are you calling this code somewhere else and it's really never stopping in some other part?

If you just mean that it's drawing too many half-circles (4, when you want 2 to make an S ), that's because of the 2 in your for-loop for x in range(2) : that for-loop has two half-circles in it, so when the loop runs twice (because of range(2) ), you get 2 * 2 = 4 half-circles. [BTW, as a convention, we generally use a single underscore _ to indicate "throw-away" variables. You'll see that the var x does not actually get used in your for-loop, it's just necessary to state some var for the for-loop syntax. A lot of Python programmers just write for _ in range(2) as a way of saying, "Don't pay attention to this var, it's not going to get used."]

So if you change the for-loop from range(2) to being range(1) , you get a single pair of half-circles and the program halts on this image:

Which, admittedly, is not a great S shape, but it's getting there. In general, drawing symbols is hard . I think a really good S is probably the hardest one. I think the easiest might be a 5 ? The best approach to figuring out how to code symbols is to draw it very large and very carefully on graph paper, then break it down into its component parts. Let's use 5 as an example, working from bottom to top:

• A curved section, maybe half-circle, maybe more like 2/3's of a circle, maybe more of an ellipse, kinda hard to be certain.
• A straight line going (mostly) up (or maybe just a hair to the right)
• A straight line going directly right, a little longer than the previous line

Then, with that series of motions in mind, create code to draw each piece on its own . Once you've done that, just have the turtle draw the first piece, then immediately draw the next, then the next. You'll have to figure out how to reset the turtle's direction between pieces, but other than that, you'll have a 5 ! It's not so much that you want to have nonlinear and linear segments together , as a single symbol is created by drawing one segment after another, and you just write code that draws the specific segment one at a time.