使用turtle库的函数turtle.left()和turtle.fd()绘制一个b边长为200的太阳花

可以按照以下步骤绘制b边长为200的太阳花：

1. 导入turtle库并创建画布窗口

import turtle

# 创建画布窗口
window = turtle.Screen()
window.title("Sunflower")

2. 创建一个turtle对象，并设置画笔颜色和粗细

# 创建一个turtle对象
sunflower = turtle.Turtle()
# 设置画笔颜色和粗细
sunflower.pensize(3)
sunflower.pencolor("red")

3. 绘制太阳花的花瓣，每个花瓣由4个线段组成，每个线段长度为b/4，绘制完成后逆时针旋转60度

# 绘制太阳花的花瓣
b = 200
for i in range(6):
    for j in range(4):
        sunflower.fd(b/4)
        sunflower.left(90)
    sunflower.left(60)

4. 绘制太阳花的中心，绘制一个半径为b/8的圆

# 绘制太阳花的中心
sunflower.pencolor("yellow")
sunflower.penup()
sunflower.goto(0,0)
sunflower.pendown()
sunflower.begin_fill()
sunflower.circle(b/8)
sunflower.end_fill()

5. 隐藏turtle对象并保持画布不关闭

# 隐藏turtle对象并保持画布不关闭
sunflower.hideturtle()
turtle.done()

完整代码如下所示：

import turtle

# 创建画布窗口
window = turtle.Screen()
window.title("Sunflower")

# 创建一个turtle对象
sunflower = turtle.Turtle()
# 设置画笔颜色和粗细
sunflower.pensize(3)
sunflower.pencolor("red")

# 绘制太阳花的花瓣
b = 200
for i in range(6):
    for j in range(4):
        sunflower.fd(b/4)
        sunflower.left(90)
    sunflower.left(60)

# 绘制太阳花的中心
sunflower.pencolor("yellow")
sunflower.penup()
sunflower.goto(0,0)
sunflower.pendown()
sunflower.begin_fill()
sunflower.circle(b/8)
sunflower.end_fill()

# 隐藏turtle对象并保持画布不关闭
sunflower.hideturtle()
turtle.done()