Basic explanation of turtle module - draw curve

stay 《Turtle Detailed explanation of module foundation - Draw a straight line 》 in , We have introduced how to import turtle Library and use turtle Library to draw straight line graphics . This article will continue turtle Library high-level usage , How to use turtle Draw curve graph .

1. The little turtle draws the same tangent circle

The characteristic of tangent circles is that each circle starts from the same place , It can be seen as finding a circle center on the left or right side of the little turtle , With r Rotate for radius 360°, The difference is that the radius of each rotation is different .

#  Import turtle library 
import turtle

#  Set the window size and initial position 
turtle.setup(700, 400, 200, 200)
#  Set the brush thickness 
turtle.pensize(4)
#  Set brush color 
turtle.pencolor("red")
#  Rotate the brush to the right 90°
turtle.right(90)
#  Bring up the brush 
turtle.penup()
#  Brush back 20px
turtle.fd(-20)
#  The paintbrush falls 
turtle.pendown()
#  Return to zero in the forward direction 
turtle.seth(0)
#  Find a circle center on the left side of the turtle and draw a radius of 40px The circle of 
turtle.circle(40)
#  Find a circle center on the left side of the turtle and draw a radius of 60px The circle of 
turtle.circle(60)
#  Find a circle center on the right side of the turtle and draw a radius of 60px The circle of 
turtle.circle(-60)
#  Set the brush color to green 
turtle.color("green")
#  Find a circle center on the right side of the turtle and draw a radius of 40px The circle of 
turtle.circle(-40)
#  Find a circle center on the left side of the turtle and draw a radius of 80px The circle of 
turtle.circle(80)
#  Find a circle center on the right side of the turtle and draw a radius of 80px The circle of 
turtle.circle(-80)

#  Program end 
turtle.done()

Relevant knowledge in the above procedures ：

1）turtle.pensize() You can set the thickness of the brush , Fill in numbers in brackets ;

2）turtle.pencolor() You can set the brush color , Fill in the color library in brackets ;

3）turtle.penup() and turtle.down() They are lifting the brush and putting it down , When the brush is lifted, the movement will not leave traces on the canvas ;

4）turtle.seth() Only change the direction of the turtle （ The angle is counterclockwise ）, But don't move forward , Angle in brackets ;

5）turtle.circle(radius, extent, steps) You can draw a circle , The first parameter radius It's the radius of the circle , It could be negative , The starting coordinate of the brush is （0, 0）, The coordinates of the center of the circle are （0, radius）; The second parameter  extent Is the size of the center angle , It can also be negative ; The third parameter steps It's the step length , Indicates that the starting point to the end point is composed of several lines , The greater the numerical , The rounder the circle is drawn .

2. Little turtle draws a curve

Conventional curves can be understood as circular segments , Use loops and circles to , Draw a curve on the screen .

#  Import turtle library 
import turtle

#  Set the window size and initial position 
turtle.setup(650, 350, 200, 200)
#  Bring up the brush 
turtle.penup()
#  Brush back 20px
turtle.fd(-250)
#  The paintbrush falls 
turtle.pendown()
#  The brush thickness is set to 15
turtle.pensize(15)
#  Brush color is blue
turtle.pencolor("blue")
#  The way forward is -40°
turtle.seth(-40)
#  Use for Cycle draw waves 
for i in range(4):
    turtle.circle(40, 80)
    turtle.circle(-40, 80)
turtle.circle(40, 80 / 2)
#  Brush forward 40
turtle.fd(40)
#  A circle 
turtle.circle(16, 180)
#  Brush forward 
turtle.fd(40 * 2 / 3)

#  Program end 
turtle.done()