Why does the code below when executed say NameError: name 'n' is not defined?

Question

from swampy.TurtleWorld import *

world = TurtleWorld
bob = Turtle()

def polyline(t, n, length, angle):
    """Draws n line segments.
    t: Turtle object
    n: number of line segments
    length: length of each segment
    angle: degrees between segments
    """
    for i in range(n):
        fd(t, length)
        lt(t, angle)

def polygon(t, n, length):
    """Draws a polygon with n sides.
    t: Turtle
    n: number of sides
    length: length of each side.
    """
    angle = 360.0/n
    polyline(t, n, length, angle)

polygon(bob, n=7, length=70)

Answer 1

The code you posted does not produce the error you have described. If I run your code verbatim, I get:

Traceback (most recent call last):
  File "foo.py", line 26, in <module>
    polygon(bob, n=7, length=70)
  File "foo.py", line 24, in polygon
    polyline(t, n, length, angle)
  File "foo.py", line 14, in polyline
    fd(t, length)
  File "/home/lars/tmp/runtime/lib/python2.7/site-packages/swampy/TurtleWorld.py", line 185, in fd
    if self.pen and self.world.exists:
AttributeError: 'NoneType' object has no attribute 'exists'

It looks like this is due to an error in your code. You have:

world = TurtleWorld

But swampy.world.TurtleWorld.TurtleWord is a class and needs to be instantiated:

world = TurtleWorld()

With this change in place, the code runs correctly and produces:

Answer 2

You have initialized the world wrongly and aren't calling class functions properly. In order to make it work, you need assign the world for your turtle, not just somewhere randomly, and call the fd and lt functions as t.fd(length) and t.lt(angle) . If you don't understand why you need to do it this way, you can try to read something like this

from swampy.TurtleWorld import *

bob = Turtle()
bob.world = TurtleWorld()

def polyline(t, n, length, angle):
    """Draws n line segments.
    t: Turtle object
    n: number of line segments
    length: length of each segment
    angle: degrees between segments
    """
    for i in range(n):
        t.fd(length)
        t.lt(angle)

def polygon(t, n, length):
    """Draws a polygon with n sides.
    t: Turtle
    n: number of sides
    length: length of each side.
    """
    angle = 360.0/n
    polyline(t, n, length, angle)

polygon(bob, 7, 70)

EDIT: larsks's solution works too, I changed the order of initializing bob and world when copy-pasting it to my file, so it didn't work for me, but he is right in this. I guessed I need to assign the TurtleWorld to turle since I was working directly with the source code for TurtleWord , where the initializing for Turtle() is like

def __init__(self, world=None):
    Animal.__init__(self, world)

so I determined using TurtleWorld() as an attribute of turtle and then directly working with member functions ( fd and lt ) was better.

Answer 3

well for the n problem, i made na raw_input, that worked for me. You could try doing that.