Python: Graphing with turtles

You can use the turtle tool to make graphs and data visualizations.

Let's say we wanted to draw a simple line, the kind that you may have seen in math class—described by a function that looks like this: y = mx + b.

We could do that with the turtle tool by defining x and y as variables in python. x will be defined as a domain of points that we want to graph across.

for i in range(-250, 250):

    #define x in terms of i
    x = i/10.0

Then, we can define y using the line equation. In this case, m = 2 and b = 3.

# define y in terms of x
y = 2x + 3

Once we have x and y defined as the coordinates of the next point on our graph, we can tell the turtle to go to that location to graph our function.

# check if y is a number, then goto(x, y)
if(not math.isnan(y)) :
    pen.goto(x, y)
    pen.pendown()

Here is the full code and demo.

import turtle, math

pen = turtle.Turtle()
pen.penup()
pen.speed(0)
pen.color("blue")

# loop through the domain
for i in range(-100,100) : 
    
    # define x in terms of i
    x = i/10.0 
   
    # define y in terms of x 
    y = 2*x + 3
    
    # check if y is a number, then goto(x, y)
    if(not math.isnan(y)) :
        pen.goto(x, y)
        pen.pendown()

Now that you have the concept down, take a look at another example. This time, we will graph a parabola.

import turtle, math

pen = turtle.Turtle()
pen.penup()
pen.speed(0)
pen.color("green")

# loop through the domain
for i in range(-100,100) : 
    
    # define x in terms of i
    x = i/10.0 

    # define y in terms of x (our parabola function)
    y = x**2 - 100
    

    # check if y is a number, then goto(x,y)
    if(not math.isnan(y)) : 
        pen.goto(x, y)
        pen.pendown()