Python turtle.backward函数代码示例

def turtle_init():
	turtle.ht()
	turtle.up()
	turtle.speed(0)
	turtle.left(90)
	turtle.backward(350)
	turtle.down()

def basaDon():
    turtle.penup()
    turtle.backward(200)
    turtle.right(90)
    turtle.forward(100)
    turtle.left(90)
    turtle.pendown()

def main():
    turtle.left(90)
    turtle.up()
    turtle.backward(120)
    turtle.down()
    drawTree(60)
    turtle.exitonclick()

def backward(seconds):
    turtle.backward(seconds * 100)
    motor_on(LEFT_BACKWARD)
    motor_on(RIGHT_BACKWARD)
    sleep(seconds)
    motor_off(LEFT_BACKWARD)
    motor_off(RIGHT_BACKWARD)

def player1_symbol(jogada):
    if jogada == 1:
        go_to(-200,200,45)
    elif jogada==2:
        go_to(0,200,45)
    elif jogada==3:
        go_to(200,200,45)
    elif jogada==4:
        go_to(-200,0,45)
    elif jogada==5:
        go_to(0,0,45)
    elif jogada==6:
        go_to(200,0,45)
    elif jogada==7:
        go_to(-200,-200,45)
    elif jogada==8:
        go_to(0,-200,45)
    elif jogada==9:
        go_to(200,-200,45)
        
    turtle.pencolor('green')
    for i in range(4):
        turtle.forward(75)
        turtle.backward(75)
        turtle.right(90)

def drawTree(tree, angle, length, width):
    turtle.width(width)

    if tree[0] == "ancestor":
        # left branch
        turtle.left(angle)
        turtle.forward(length)
        turtle.right(angle)
        drawTree(tree[1], angle - 0.2 * angle, length - 0.2 * length, width - 0.3 * width)
        turtle.width(width)
        turtle.left(angle)
        turtle.backward(length)
        turtle.right(angle)
        
        # right branch
        turtle.right(angle)
        turtle.forward(length)
        turtle.left(angle)
        drawTree(tree[2], angle - 0.2 * angle, length - 0.2 * length, width - 0.3 * width)
        turtle.width(width)
        turtle.right(angle)
        turtle.backward(length)
        turtle.left(angle)
    else:
        # draw the ending node
        turtle.pencolor("red")
        turtle.write(tree[0], font=("Monospace", 14, "bold"))
        turtle.pencolor("black")

def pezzo(color, colors = colors, unit = unit, alfa = alfa, depth = depth):
    turtle.pencolor(colors[color])
    turtle.fillcolor(color)
    turtle.begin_fill()
    for i in range(2):
        turtle.forward(unit)
        turtle.left(90)
        turtle.forward(unit)
        turtle.left(90)
    turtle.forward(unit)
    for i in range(2):
        turtle.left(alfa)
        turtle.forward(depth)
        turtle.left(alfa)
        turtle.forward(unit)
        turtle.left(90)
    turtle.backward(unit)
    turtle.left(90)
    turtle.forward(unit)
    turtle.right(90)
    for i in range(2):
        turtle.forward(unit)
        turtle.left(alfa)
        turtle.forward(depth)
        turtle.left(180-alfa)
    turtle.end_fill()
    turtle.right(90)
    turtle.forward(unit)
    turtle.left(90)

def pythagoras_tree(size, n):
    turtle.begin_fill()
    for _ in range(4):
        turtle.forward(size)
        turtle.left(90)

    turtle.end_fill()
    if n > 0:
        roof = .5 * math.sqrt(2) * size

        turtle.left(90)
        turtle.forward(size)
        turtle.right(45)

        pythagoras_tree(roof, n - 1)

        turtle.forward(roof)
        turtle.right(90)

        pythagoras_tree(roof, n - 1)

        turtle.left(90)
        turtle.backward(roof)
        turtle.left(45)
        turtle.backward(size)
        turtle.right(90)

def tscm_backward(n):
    """Move the turtle backward a distance N units on the current heading,
    without changing direction."""
    _check_nums(n)
    _tscm_prep()
    turtle.backward(n.num_val)
    return UNSPEC

def render(tree, length, width):
    "Draws a given phylogenetic tree constrained by dimensions of" 
    "length and width."
    root = tree[0]
    leftTree = tree[1]
    rightTree = tree[2]
    if leftTree == (): 
        turtle.dot(10)
        turtle.write(root , font=("Arial", 20, "normal"))
        return
    else:
        turtle.dot(10)
        turtle.write(root, font=("Arial", 20, "normal"))
        turtle.left(90)
        turtle.forward(width)
        turtle.right(90)
        turtle.forward(length)
        render(leftTree, 0.5*length, 0.5*width) 
        turtle.back(length)
        turtle.left(90)
        turtle.backward(2*width)
        turtle.right(90)
        turtle.forward(length)
        render(rightTree, 0.5*length, 0.5*width)
        turtle.back(length)
        turtle.right(90)
        turtle.back(width)
        turtle.left(90)
        return

def draw_tree(depth, height, branches, leafs, angle):
    """
    Draws the tree using recursion
    :pre: pos(0,0), heading east, up
    :post: pos(0,0), heading east, up
    :param depth: number of layers of sub branches (recursion depth)
    :param height: height of tree
    :param branches: number of branches
    :param leafs: number of leafs
    :param angle: angle between branches
    :return: None
    """
    if depth == 0:
        leafs = random.randint(0, leafs)
        draw_leaf(leafs)
        t.down()
        pass

    else:
        t.color('brown')
        t.forward(height)
        for i in range(1, branches+1):
            t.left(90 - i * angle)
            #random branches
            branches = random.randint(branches-1,branches+5)
            draw_tree(depth - 1, height * HEIGHT_FACTOR, branches, leafs, angle)
            t.right(90 - i * angle)
            #random angle
            angle = random.randint(angle-1, angle+1)
            if depth == 1:
                break
        t.color('brown')
        t.backward(height)

def draw_tree(length=200):
    """
    A recursive function that uses the turtle external library to
    draw a binary tree in the size of the user input (or default: 200).

    The flow of the function that it first draw a straight line,
    the right side branches and then left side branches.
    """
    # length is number of pixel 
    deg = 30 # degrees of each branch (left, right)

    if not length < 10:
        # Base is when the length is lower then 10,
        # otherwise, continue with the iteration.

        turtle.forward(length)  # Draw straight line forward size length 
        turtle.right(deg)       # Turn right 30 degrees
        draw_tree(length*0.6)   # Call the recursion to draw the right
                                # side branches

        turtle.left(deg*2)      # Then turn left (30 degrees center,
                                # 30 degrees more to the left)
        draw_tree(length*0.6)   # Draw inner left side branches

        turtle.right(deg)       # Turn to center
        turtle.backward(length) # Go backwards length size

def draw_arrow():
    '''Draw an arrow toward the turtle's current heading, then return to
    position and heading.'''

    arrow_length = 7 # pixels
    arrow_width = 10 # pixels
    arrow_end = tt.position()
    old_heading = tt.heading()

    # move to back end of upper line
    tt.penup()
    tt.backward(arrow_length)
    tt.left(90)
    tt.forward(arrow_width)
    # draw upper line
    tt.pendown()
    tt.setposition(arrow_end)
    tt.setheading(old_heading)
    # move to back end of lower line
    tt.penup()
    tt.backward(arrow_length)
    tt.right(90)
    tt.forward(arrow_width)
    # draw lower line
    tt.pendown()
    tt.setposition(arrow_end)
    tt.setheading(old_heading)
    tt.penup()

def house(length):
    """
    Draw a nice house where the base is length long and put the turtle
    back to its original position at the end.
    """
    inside = SQRT2 * length
    roof = inside / 2.

    turtle.forward(length)
    turtle.left(90)
    turtle.forward(length)

    # roof
    turtle.left(45)
    turtle.forward(roof)
    turtle.left(90)
    turtle.forward(roof)
    turtle.left(45)

    # interior
    turtle.forward(length)
    turtle.left(135)
    turtle.forward(inside)
    turtle.left(135)
    turtle.forward(length)
    turtle.left(135)
    turtle.forward(inside)

    # back into position
    turtle.left(45)
    turtle.backward(length)

		def plot_a_face(angle, pencolor, fillcolors, dimension):
			t.down()
			
			def plot_a_row(angle, pencolor, fillcolors,dimension):
				for i in range(len(fillcolors)):
					t.color(pencolor, fillcolors[i])
					t.begin_fill()
					t.forward(50*3/dimension)
					t.right(angle)
					t.forward(50*3/dimension)
					t.right(180 - angle)
					t.forward(50*3/dimension)
					t.right(angle)
					t.forward(50*3/dimension)
					t.right(180 - angle)
					t.end_fill()
					t.forward(50*3/dimension)
			
			n = int(len(fillcolors)/dimension)
			for i in range(n):
				plot_a_row(angle,pencolor,fillcolors[dimension*i:dimension*(i+1)],dimension)
				t.up()
				t.backward(150)
				t.right(angle)
				t.forward(50*3/dimension)
				t.left(angle)
				t.down()