Python输入输出练习，运算练习，turtle初步练习

1. Hello World！

   1. print("Hello World!!")

2. 简单交互（交互式，文件式）教材P19

   1. name=input("what is your name?\n")
      where=input("where are you now?\n")
      age=input("how old are you ?\n")
      print("your name is {}".format(name))
      print("you live in {}".format(where))
      print("you are {} years old".format(age))

3. 用户输入两个数字，计算并输出两个数字之和：

   1. num1=input("input a number:\n")
      num2=input("input an other number:\n")
      print(sum,end="")
      sum=num1+num2

4. 用户输入三角形三边长度，并计算三角形的面积：（海伦公式）

5. a = float(input("输入第一边边长:"))
   b = float(input("输入第二边边长:"))
   c = float(input("输入第三边边长:"))
   s = (a + b + c) / 2
   area = (s*(s-a)*(s-b)*(s-c)) ** 0.5
   print("三角形面积为 %0.2f" %area)

6. 输入半径，计算圆的面积。

   pi=3.1415926
   r=float(input("请输入半径:"))
   area=pi*r*r
   print("面积为 %0.2f"%area)

7. 画一组同切圆

   import turtle
   turtle.speed(100)
   turtle.circle(10)
   turtle.circle(20)
   turtle.circle(30)
   turtle.circle(40)

8. 画一个五角星

   import turtle
   turtle.speed(100)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)

9. 画一个全黄色的五角星

   import turtle
   turtle.speed(100)
   turtle.fillcolor("yellow")
   turtle.begin_fill()
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.forward(100)
   turtle.right(144)
   turtle.end_fill()

思考：

1. 画一组同心圆。

   import turtle
   #draw first circle
   turtle.penup()
   turtle.goto(0,-200)
   turtle.pendown()
   turtle.circle(200)
   #draw second circle
   turtle.penup()
   turtle.goto(0,-150)
   turtle.pendown()
   turtle.circle(150)
   #draw third circle
   turtle.penup()
   turtle.goto(0,-100)
   turtle.pendown()
   turtle.circle(100)
   #draw fourth circle
   turtle.penup()
   turtle.goto(0,-50)
   turtle.pendown()
   turtle.circle(50)

2. 画国旗上的五个五角星