Python TurtleGraphics - Smoothing out random walks?

Question

I need some help with this question relating to TurtleGraphics in Python:

A small detail of tipsy_turtle() is that when the turtle turns 90 degrees it immediately "jumps" to the new direction. This makes its movement seem jagged. It might look better if the turtle moved smoothly when turning. So, for this question, write a function called smooth_tipsy_turtle() that is the same as tipsy_turtle(), except instead of using the turtle.right(d) function, write a brand new function called smooth_right(d) that works as follows:

 - If d is negative then
      - repeat the following -d times:
            - turn left 1 using the ordinary turtle.left command

  - Otherwise, repeat the following d times:
          - turn right 1 using the ordinary turtle.right command

Here is my original function to get the random turtle movement:

def tipsy_turtle(num_steps):
    turtle.reset()
    for step in range(num_steps):
       rand_num = random.randint(-1, 1)
       turtle.right(rand_num * 90)
       turtle.forward(5 * random.randint(1, 3))

So, how would I go about making this work? I tried adding:

   if rand_num*90 < 0:
       for step in range(rand_num*90):
           turtle.left(rand_num*90)
   else:
       turtle.right(rand_num*90)

But it didn't really work out and I don't know what I did wrong. Thanks!

Answer 1

Hopefully this sample clears up what went wrong in your example -- you performed either rand_num*90*rand_num*90 left turns, or rand_num*90 right turns!

if rand_num < 0: # don't need to multiply by 90 here - it's either +ve or -ve.
    for step in xrange(90): # xrange is preferred over range in situations like this
         turtle.left(rand_num) # net result is 90 left turns in rand_num direction
else:
    for step in xrange(90):
         turtle.right(rand_num)

Or you could write this as:

for step in xrange(90):
    if rand_num < 0:
        turtle.left(rand_num)
    else:
        turtle.right(rand_num)

For code like this, it's really a matter of preference.

Answer 2

You might be able to do without the conditional for left-vs-right. I don't have python syntax down, so here's pseudocode

turtle left randomly generated value 0 to 90
turtle right randomly generated value 0 to 90
turtle forward some amount

I.e., generate a random angle and turn left that much, then generate another random angle and turn right by that much. This way you don't have to worry about generating or dealing with negative randoms. You can keep all the random angles positive, and the combination of a left followed by a right effectively does a subtraction for you which gives a nice gaussian distribution to the changes in direction.

Answer 3

I guess I'll venture an answer even though I am not completely sure what you want (see my comment to the question, and don't be surprised if I edit this answer as appropriate!).

Assuming you want the turtle to turn some number of degrees at each step, not necessarily 90, but not more than 90, then simply use rand_num = random.randint(-90, 90) and then turtle.right(rand_num).