Python输入输出练习，运算练习，turtle初步练习

1、Hello World！
print("Hello World!")

2、简单交互（交互式，文件式）教材P19
>>> name = input("please input your name:")
>>> please input your name:Poon
>>> print(name)
>>> Poon

3、用户输入两个数字，计算并输出两个数字之和：
s1 = float(input("please input the first num:"))
s2 = float(input("please input the second num:"))
sum = s1 + s2
print("the result is:%s"  % sum)


print("the result is %.2f" %((float(input("the first num is"))) + (float(input("the secibd num is")))))

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）
a = float(input("Please input the a side:"))
b = float(input("Please input the b side:"))
c = float(input("Please input the c side:"))
p = (a + b + c)/2
s = (p *(p-a) *(p-b)*(p-c))**0.5
print("the square is:%.2f" % s)

5、输入半径，计算圆的面积。
from math import pi
r = float(input("Please input the r:"))
s = pi * (r**2)
print("the area is %.2f" % s)

6、画一组同切圆
import turtle as t
t.speed(1)
t.circle(10)
t.circle(20)
t.circle(30)

7、画一个五角星
import turtle as t
t.speed(1)
for i in range(5):
 t.forward(100)
 t.right(144)

8、画一个全黄色的五角星
import turtle as t
t.fillcolor("red")
t.begin_fill()
while True:
    t.forward(200)
    t.right(144)
    if abs(pos())<1:
        break
t.end_fill()