Turtle Library

We start learning python in a fun way by using python turtle graphic library.

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Basic

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Firstly we import turtle library

from turtle import *
# turtle is the library
# * is the global variable

move forward

fd() # let turtle forward any step
eg: fd(100) # forward 100 steps

move backward

bk() # let turtle backward any step
eg: bk(100) # backward 100 steps

turn right

rt() # rotate right any degree
eg: rt(90) # rotate right 90 degree

turn left

lt() # rotate left any degree
eg: lt(90) # rotate left 90 degree

draw a circle

cricle()
# value is radius and it can be positive or negative integer(20,30, -33...) or decimal(9.3, -32.33...)
circle(100)
# if the value is positive, it's a anticlockwise circle
circle(40.56)
# if the value is negative, it's a clockwise circle

set pen color

() # set pen color
eg1: color('red') # set pen color by color name
eg2: color(119, 171, 170) # set pen color by RGB value
eg3: color('#77abaa') #s et pen color by color code

set background color

bgcolor() # set background color
eg: bgcolor('green') # set background color green

set turtle moving speed

speed() # set turtle moving speed
speed(10)
# The number can be from 1 to 10 and has to be a whole number.
# You cannot have for example 4.7 as the number.
# Setting it above 10 will cause the speed to not work.

set pen size

pensize()
pensize(5)

go to the specic position

goto(x, y)
# x and y are coordinates in the graphic

fill color

fillcolor('blue') # set filling color
begin_fill() # set current position as the beginning position to fill in color
... code here ...
end_fill() # set current position as the end position to finish filling
fillcolor('red')
begin_fill()
circle(90)
end_fill()

pen up & pen down

penup() # pen up - not drawing
pendown() # pen down - drawing

clear all drawing

clear()

draw word

write('Hello')

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Exercise 1: Draw a running windmill with 8 parts.

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# solution:

speed(100)

for i in range(8):
    fd(100)

for i in range(3):
    fd(100)
    rt(120)
    bk(100)
    rt(45)

Repeat

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for loop

for i in range(10):
    print(i)
#repeat 10 times
# 4 spaces indent
# i is the changing variable which can be any name
# i changes from 0 to 9 which is 0->1->2->3->4->5->6->7->8->9
for i in range(2,4):
    print(i)
#i changes from 2 to 3 which is 2->3
for i in range(2,10,3):
    print(i)
#i changes from 2 to 9 by 3 which is 2->5->8
#Don't forget semicolon and indent(4 spaces)

Function

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function - draw a square

def square():
    for i in range(4):
        fd(100)
        rt(90)

function - draw a triangle

def tri():
    for i in range(3):
        fd(100)
        rt(120)

function - draw a polygon

def poly(n):
    for i in range(n):
        fd(30)
        lt(360/n)

main() function

if __name__ == "__main__": #python syntax for main() function entrance
    square()
    traingle()
    poly()

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DIY your own function

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Exercise 2: Draw 27 polygons from triangle to the polygon with 30 edges.

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# solution:

def poly(n):
    for i in range(n):
        fd(30)
        lt(360/n)

def pic():
    for i in range(3,30):
        poly(i)

pic()